Astronomy news april 2016

www.Astronomy.com

Vol. 4

4 • Issu

e 4

APRIL 2016

New missions mine asteroid secrets p. 28

How to image

JUPITER p. 56

Where is amateur astronomy heading? p. 61 Sky-Watcher USA’s hot new scope tested p. 64

PLUS!

FINALLY! The historic journey to

EUROPA p. 22

The world’s best-selling astronomy magazine

Starmus celebrates Stephen Hawking’s legacy p. 50

Untangling the magnetic universe p. 44

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CONTENTS

4 ASTRONOMY • APRIL 2016

22 COVER STORYInside the historic mission to Europa Ater decades of canceled mis-

sions and false starts, NASA is

inally headed for Carl Sagan’s

dream destination. ERIC BETZ

28New missions mine asteroid secrets When Rosetta landed on a comet,

the world held its breath. Now

scientists are about to attempt an

even more ambitious mission —

twice. ELIZABETH TASKER

34Ask AstroExpansion explained.

36The Sky this MonthMARTIN RATCLIFFE AND

ALISTER LING

38StarDome and Path of the PlanetsRICHARD TALCOTT;

ILLUSTRATIONS BY ROEN KELLY

44Untangling the magnetic universe his powerful but mysterious

force plays a fundamental role

in shaping galactic structure and

allowing stars to form.

YVETTE CENDES

50Celebrating Stephen Hawking’s legacyScientists, astronauts, musicians,

and the public will come to the

Canary Islands this summer for a

tribute to the renowned physicist.

DAVID J. EICHER

56How to image Jupiter Longtime planetary photogra-

pher CHRISTOPHER GO guides you

step by step through the process

of imaging this gas giant.

61Where is amateur astronomy heading? Today’s trends will lead amateur

astronomy to a better and more

popular future. KEVIN RITSCHEL

AND MARIA GRUSAUSKAS

64Sky-Watcher USA’s hot new scope tested Combine 5 inches of light-

gathering power with easy porta-

bility, and you have a winner of a

scope. RAYMOND SHUBINSKI

COLUMNSStrange Universe 10BOB BERMAN

For Your Consideration 14JEFF HESTER

Secret Sky 18STEPHEN JAMES O’MEARA

Observing Basics 20GLENN CHAPLE

Astro Sketching 66ERIKA RIX

Cosmic Imaging 68ADAM BLOCK

QUANTUM GRAVITYSnapshot 9

Astro News 12

IN EVERY ISSUEFrom the Editor 6

Letters 10, 18, 20

New Products 67

Advertiser Index 70

Reader Gallery 72

Breakthrough 74

FEATURES

APRIL 2016VOL. 44, NO. 4

28

Astronomy (ISSN 0091-6358, USPS 531-350) is published monthly by Kalmbach Publishing Co., 21027 Crossroads Circle, P. O. Box 1612, Waukesha, WI 53187–1612. Periodicals post-age paid at Waukesha, WI, and additional offices. POSTMASTER: Send address changes to Astronomy, P.O. Box 62320, Tampa, Fla. 33662-2320. Canada Publication Mail Agreement #40010760.

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ON THE COVER Europa’s fractured surface beckons to astrobiologists. What creatures might swim in its salty seas?

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B Y D A V I D J . E I C H E R

FROM THE EDITOREditor David J. EicherArt Director LuAnn Williams Belter

EDITORIAL

Managing Editor Kathi Kube Senior Editors Michael E. Bakich, Richard TalcottAssociate Editors Eric Betz, Korey HaynesCopy Editors Dave Lee, Elisa Neckar Editorial Associate Valerie Penton

ART

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CONTRIBUTING EDITORS Bob Berman, Adam Block, Glenn F. Chaple, Jr., Martin George, Tony Hallas, Phil Harrington, Jeff Hester, Liz Kruesi, Ray Jayawardhana, Alister Ling, Steve Nadis, Stephen James O’Meara, Tom Polakis, Martin Ratcliffe, Mike D. Reynolds, Sheldon Reynolds, Erika Rix, Raymond Shubinski

EDITORIAL ADVISORY BOARD

Buzz Aldrin, Marcia Bartusiak, Timothy Ferris, Alex Filippenko,Adam Frank, John S. Gallagher lll, Daniel W. E. Green, William K. Hartmann, Paul Hodge, Anne L. Kinney, Edward Kolb, Stephen P. Maran, Brian May, S. Alan Stern, James Trefil

Kalmbach Publishing Co.President Charles R. CroftVice President, Editorial Kevin P. KeefeSenior Vice President, Sales & Marketing Daniel R. LanceVice President, Consumer Marketing Nicole McGuire Editorial Director Diane M. BachaCorporate Art Director Maureen M. SchimmelArt and Production Manager Michael SolidayCorporate Advertising Director Ann E. SmithSingle Copy Specialist Kim Redmond

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For years, astronomy

enthusiasts have noticed

the graying of our

hobby. As with other

serious fields, amateur

astronomy meetings and

star parties over the past

decade have trended toward

an older crowd, with largely

the same faces showing up

at the same events.

Where are the young peo-

ple? This question echoes

throughout the chambers of

astronomy clubs and star

party organizers across the

United States and the world.

On p. 61, two enthusiastic

amateur astronomers —

Kevin Ritschel and Maria

Grusauskas, one veteran and

one youngster — ask, “Where

is amateur astronomy going?”

Their commentary will no

doubt provide you with some

intriguing thoughts.

The amateur astronomy

hobby hasn’t necessarily

gone anywhere, but like

other areas of interest, it’s in

the midst of dramatic, whirl-

wind change. The print cir-

culation of Astronomy has

held relatively steady at

about 100,000, keeping it the

most-read astronomy maga-

zine in the world — a title it

has held since 1981. Our

website attracts about

400,000 unique visitors per

month. On Twitter, we have

65,000 followers. Our

Facebook following has

grown to 1.16 million. So

altogether we have the larg-

est audience of astronomy

enthusiasts on Earth.

The notion about young

people disappearing from

amateur astronomy is a false

one. It’s true that far fewer

people in their teens, 20s,

and 30s are going to astron-

omy club meetings or even

to star parties compared

with a generation ago, when

I was young. But that’s not to

say they aren’t sampling and

involving astronomy, space,

and the cosmos in their lives.

Most are doing it in very

different ways.

It’s become harder for

most people to access a dark

sky. Many in society now

look through the viewfinder

of a smartphone rather than

pulling a book off a shelf and

reading it. So for many peo-

ple, the depth of interest has

dramatically changed. For

lots of folks, it’s enough to

hear a bit about their favorite

subject on TV for a half-

hour or maybe more every

week. End of story.

But astronomy, cosmol-

ogy, and planetary science

are in the midst of a modern

renaissance. The past gen-

eration has witnessed an

explosion of knowledge

about the biggest cosmic

questions humans have

posed for millennia.

The astronomy hobby is

no fad. It offers a deep and

abiding way to know the

meaning of it all around you,

and perhaps even why you’re

here on this planet in an

ordinary solar system inside

one of 100 billion galaxies we

know about.

The way amateur astron-

omy gets practiced, and the

way people participate in it,

is in rapid change. But

human understanding and

appreciation of the universe

is not going anywhere. Not

just yet.

David J. Eicher

Editor

Whither the astronomy hobby?

Follow the Dave’s Universe blog: www.Astronomy.com/davesuniverse

Follow Dave Eicher on Twitter: @deicherstar

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Earth Science

Technology

Physics & Math

Space Exploration

QGQUANTUMGRAVITY

EVERYTHING YOU NEED TO KNOW ABOUT THE UNIVERSE THIS MONTH . . .

W W W.ASTRONOMY.COM 9

SNAPSHOT

Musings on the nearest starWhat can Alpha and Proxima Centauri tell us?

If you or I had a spare 75,000 years and

a few trillion dollars set aside, we could

try journeying to the closest star beyond

the Sun, Alpha Centauri. Some 4.3 light-

years away, this triple star system is more

representative of stars in the galaxy than

our loner Sun. Alpha Centauri consists

of a bright double star, Alpha A and

Alpha B, and a distantly orbiting red

dwarf called Proxima Centauri, which is

a shade closer to us at 4.2 light-years.

Alpha Centauri is one of the most bril-

liant stars in the southern sky, shining at

magnitude 0. It is prominently visible to

the naked eye as the luminary of

Centaurus, nestled near the bright con-

stellation Crux the Southern Cross.

Of the double star components, Alpha

Cen A is a sunlike star that is slightly

larger and more luminous than our star.

Alpha Cen B is slightly smaller and dim-

mer than the Sun and also slightly more

orange in hue. Proxima is a small, red-

dish star with only one-tenth the mass of

the Sun, or 129 times the mass of Jupiter.

Proxima orbits its two larger companions

once every half-million years.

If you observe from the southern sky

or get a chance to travel there, make sure

you look at this trio of suns. They are a

reminder of both the relative closeness of

objects in the universe and its incredibly

large distance scale. — David J. Eicher

HOT BYTES >>TRENDING

TO THE TOP

AURORA EXPLORER

NASA launched its RENU 2 rocket into the thermo-sphere above Norway for an in situ study of the complex physics behind the northern lights.

LUNAR STRIKES

NASA’s LADEE spacecraft watched meteoroids hit the Moon and vapor-ize, spiking sodium and potassium levels in its hint of an atmosphere.

BLACK HOLE MAX

In a study titled “How big can a black hole grow?,” scientists say a size any bigger than 50 billion suns would extinguish the black hole’s disk.

The closest star to the Sun, Alpha Centauri, appears as a dramatically bright blue-white blob in this long exposure from the Digitized Sky Survey 2. The triple star system lies about 4.3 light-years away, some 25 trillion miles (40 trillion kilometers).

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Some areas of sci-

ence advance in

increments. We

see slow evolution-

ary improvements

in aeronautical engineering

and medical discoveries. But

astronomy is different. Here,

the universe often leaps out

and goes boo! So let’s use April

Fool’s Day as our excuse to

review the top 20 “pranks” the

cosmos has sprung on us.

Start with Galileo. Since no

one had pointed a telescope at

the sky before, he was bound to

get surprises. Nobody had fore-

seen lunar craters or moons

going around other planets

like Jupiter, as he observed. But

when he looked at Saturn, he

entered the Twilight Zone. On

Earth, there’s no example of a

ball surrounded by unattached

rings. This was beyond human

experience. No wonder it took

two centuries for anyone to

deduce that they’re neither

solid nor gaseous, but made of

separate moonlets. So our first

April Fool’s prank? Saturn’s

glorious rings.

Fast forward to 1781. That’s

when William Herschel first

peered at a bizarre green ball.

No one had discovered any

planets beyond the five bright

ones since prehistory. No great

thinker, no holy book, no

philosopher had done more

than idly speculate about more

planets out there in our solar

system. Herschel’s spotting of

Uranus was the most unex-

pected and amazing discovery

of all time.

Surprise No. 3 stays with

Herschel. Nineteen years after

finding Uranus, he discovered

the first-ever invisible light.

Light we cannot see?

STRANGEUNIVERSE

How cosmic surprises keep blowing our minds.

B Y B O B B E R M A N

April Fool’s!

FROM OUR INBOX

It astonished the world. The

bulk of the Sun’s emissions are

invisible “calorific rays.” Late

that century, people started

calling it infrared.

We have to credit Albert

Einstein with several mind-

blowers. First, that space and

time both shrink or grow

depending on the observer’s

conditions. This means the uni-

verse does not have a fixed size.

And a million years elapse in

one place while a single second

is experienced by someone else

— at the same time. Did any-

one see that coming? Do most

people grasp this even today?

As if that wasn’t enough mind

twisting, he showed that solid

objects and energy are two faces

of the same entity.

Jump ahead to 1920. That’s

when Arthur Eddington fig-

ured out what makes the stars

shine. Imagine: a new type of

“burning.” An alchemic change

of one element to another. This

nuclear fusion process is so

efficient that each second the

Sun emits the energy of 96 bil-

lion 1-megaton H-bombs. Sure,

physicists knew the Sun couldn’t

create light and heat by burning

in the usual way. But this?

A few years later, Edwin

Hubble announced that all

those spiral nebulae were sepa-

rate “island universes.” Granted,

this had been suspected by half

of all astronomers for decades.

It was not a sudden April Fool’s.

Still, bam, the universe officially

became unspeakably larger than

it was before. That’s gotta count

as a boo! event.

Then the quantum gang rode

into town. Their revelations

were astonishing. Empty space

seethes with energy. A bit of

matter can know what another

is doing and react instanta-

neously across the universe as if

no space exists between them.

An observer’s presence influ-

ences the experiment.

In 1930 came the predic-

tion for a new tiny entity, the

neutrino. It’s the universe’s

most common particle. Five

trillion zoom through your

tongue every second. The 1936

discovery of the subatomic

muon was equally unexpected.

It famously made Nobel Prize

winner Isidor Rabi say, “Who

ordered that?”

The 1967 discovery of the

first neutron star revealed

a sun smaller than Hawaii,

whose material is so dense that

each speck equals a cruise ship

crushed down to the size of the

tip of a ballpoint pen. And that

was a double whammy because

it was also the first pulsar. Did

any genius foresee that some

stars could spin hundreds of

times a second?

The surprises haven’t let

up. A microwave background

energy filling all space? A solid

Pluto-size ball in the middle

of our planet, spinning faster

than the rest of Earth? And

what about the enormous

hexagon at Saturn’s north pole?

Or the fact that cosmic “rays”

are overwhelmingly protons?

1998 brought astronomers

another stunner. When the

universe was half its pres-

ent age, all its galaxy clusters

simultaneously started mov-

ing faster. It’s as if stupendous

rocket engines fired simultane-

ously everywhere in the cos-

mos. We don’t know anything

about this antigravity force —

but we now call it dark energy.

Then in 2010, the Fermi

gamma ray telescope found

two ultra high-energy spheres,

each 25,000 light-years across,

occupying half of our southern

sky. The entities meet tangen-

tially at our galaxy’s core like

an hourglass. They’re violent

and utterly baffling.

We’re out of room, but the

universe never is. For the cos-

mos — and we who explore it —

it’s always April Fool’s.

BROWSE THE “STRANGE UNIVERSE” ARCHIVE AT www.Astronomy.com/Berman.

Contact me about my strange universe by visiting

http://skymanbob.com.

“THE UNIVERSE OFTEN LEAPS OUT

AND GOES BOO!”

KudosI’ve been reading Astronomy magazine for years, and the

December issue is by far the best. What a terrific job of putting the

universe in perspective — no easy task. It is an absolutely stunning

combination of writing, photos, and graphics. Congratulations

David Eicher and every single member of your staff.

— David Davidson, Atlanta

Beautiful diagramsYou really outdid yourself this time. The December issue was

outstanding! The graphics that accompanied the clearly written

text were both beautiful and informative. The diagrams of the

Local Group on p. 47 and the Local Supercluster on p. 53 are

amazing and put everything into perspective. I keep going back

to them trying to visualize the immensity of space they portray

and then realize that even the supercluster graphic would turn

into a pinpoint when superimposed on the greater fabric of our

universe. Keep up the great work!

— Robert Bobo, McKenzie, Tennessee

WWW.ASTRONOMY.COM 11

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ASTRONEWS

FAST FACT

NEW MOON ROCKS. China’s Yutu rover has found a new kind of lunar rock. The first spacecraft to explore the Moon since Apollo found titanium levels unlike anything astronauts brought back. The finding could ultimately help explain the Moon’s formation.

BRIEFCASE

NEW SOLAR SYSTEM PLANET RUMORS

WAX AND WANEAstronomers from Sweden and Mexico made waves

December 8 when they submitted a paper claiming the existence of an object that might be a super-Earth in

the outer solar system. Their conclusion was based on two observations showing a source zooming across the sky. Only close objects move so quickly. But reanalysis

discredited one of their two observations, leaving them with only a single snapshot and no knowledge of any

change with time, therefore calling the source’s proxim-ity into question as well. The team withdrew their paper

for now, but their remaining observation is strong, so they continue investigating their mysterious find.

•VLA HELPS UNWRAP

SOLAR FLARE QUESTIONSScientists used the Very Large Array (VLA) to study

bursts of radio waves that accompanied a solar flare in 2012. Solar flares are bright bursts of energy sometimes accompanied by coronal mass ejections (CMEs), which are eruptions of charged material from the Sun’s sur-face. Scientists had theories about how flares could

accelerate the material from a CME, but supporting evi-dence was scarce. The VLA revealed that the location of

radio bursts matches a predicted shock region where electrons are whipped into speeds high enough to

cause the powerful energy release of a CME, matching computer simulations. — Korey Haynes

On December 11, astronomers used the

Hubble Space Telescope to image for the

first time a supernova at the place and

time they predicted it would appear.

The project began after the Grism Lens

Amplified Survey from Space and

Hubble’s Frontier Fields program cap-

tured the distant galaxy cluster MACS

J1149+2223, creating multiple images of a

supernova around a large elliptical galaxy.

Astronomers refer to this process as gravi-

tational lensing. The cluster lies some 5

billion light-years from Earth, and the

supernova is roughly twice as far away.

“It really threw me for a loop when I

spotted the four images surrounding the

galaxy — it was a complete surprise,” said

Patrick Kelly of the University of

California, Berkeley, lead author on the

supernova discovery paper.

The real surprise came when the

astronomers predicted — and then cap-

tured — a fifth image of the supernova.

This was possible because the matter

within the galaxy cluster has an uneven

distribution, so the supernova’s light can

take different paths to our instruments.

“We used seven different models of the

cluster to calculate when and where the

supernova was going to appear in the

future,” explains Tommaso Treu, lead

author of the modeling comparison paper,

from the University of California at Los

Angeles, “and remarkably all predicted

approximately the same time frame for

when the exploding star would appear.”

After the predictions were in hand, the

team used Hubble starting at the end of

October to monitor the galaxy cluster

periodically. And on December 11, the

supernova reappeared as a fifth gravita-

tionally lensed image.

The astronomers have nicknamed the

supernova “Refsdal” in honor of

Norwegian astrophysicist Sjur Refsdal,

who did pioneering work on how gravita-

tional lensing could help scientists study

the universe’s expansion. — Michael E. Bakich

SUPERNOVA

PREDICTION

LEADS TO IMAGE

STAR SIZES

After multiple tries since 2013 and a total launch failure last June that temporarily grounded the private company, SpaceX suc-ceeded in landing its Falcon 9 rocket after launch on December 21. This is the first success-ful example of a fully reusable rocket system that can deliver cargo to low-Earth orbit.

This particular rocket will likely be retired as a museum treasure, but it survived its journey intact, delivered 11 satellites to orbit, and passed subsequent ground tests. Rival company Blue Orbital achieved its own rocket landing only a month earlier, but for a suborbital flight, which substantially eases the requirements compared with SpaceX’s low-Earth orbit achievement. Both companies hope that reus-able rockets will make commercial space flight cheaper and more viable. — K. H.

The Falcon has landed

White dwarf

0.01

Range = 0.08 to 0.62

Red dwarf

Sun

1

Red giant

20

100

Although Arcturus (Alpha [α] Boötis) is often called a red giant, it is, in fact, orange.

SIZE DOES MATTER. Stars arrange into five basic sizes. Sun-like stars (diameter = 1 in this graphic) are easiest to picture. But what about the others, two of which are smaller and two bigger than our Sun? ASTRONOMY:

MICHAEL E. BAKICH AND ROEN KELLY

Red giants range from 20 to 100 times the Sun’s size. On this scale, the smallest is a circle whose diameter is 26.6 inches; the largest spans 133.33 inches.

Red supergiant (not shown): 900 to 1,200

The smallest and larg-

est red supergiant stars

would form circles with

edges 600 and 800 inch-

es from the Sun’s center,

respectively.

WE GOT ONE! Hubble spotted these four projec-tions of the same supernova whose light is warped by a galaxy cluster. In December, a fifth appeared.

TOUCHDOWN. The Falcon 9’s first stage landed at Cape Canaveral on December 21 after successfully delivering 11 satellites to low-Earth orbit. SPACEX

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ASTRONEWS


Jellyfish Nebula’s inky injection created a pulsar

As NASA’s Curiosity rover ascends Mount Sharp — the 3-mile-high (5 kilometers) pile of layered sedi-mentary rock inside Mars’ Gale Crater — it continues to surprise scientists.

In mid-December, Curiosity’s sci-ence team announced the probe’s discovery of huge concentrations of silica, a rock-forming mineral made of silicon and oxygen that on Earth often appears as quartz. Some rocks contain up to 90 percent silica, dwarf-ing the levels seen on the mountain’s lower slopes.

“These high-silica compositions are a puzzle,” says team member

Albert Yen of NASA’s Jet Propulsion Laboratory in Pasadena, California. “You can boost the concentration of silica either by leaching away other ingredients while leaving the silica behind, or by bringing in silica from somewhere else. [Both] of those pro-cesses involve water.” The findings were such a surprise that scientists sent Curiosity back to the area to study it in greater detail.

Unraveling the silica mystery will forge a better understanding of Gale Crater’s history. Does the mineral’s presence signify a flow of acidic water, which would carry away other

compounds and leave silica behind? Or is it a marker for neutral or alkaline water, which could transport the dis-solved mineral into the area and then deposit it?

Curiosity drilled into one rock that adds an intriguing piece to the puz-zle. The rock contained tridymite, a type of silica rare on Earth that had never been seen before on Mars. On our planet, tridymite forms at high temperatures and often in explosive volcanic eruptions, raising the possi-bility that Gale Crater experienced volcanic activity in addition to flow-ing water. — Richard Talcott

QUICK TAKES

PARTICLE

PREMONITION Scientists using the Large Hadron Collider have seen

strange gamma-ray “bumps” that could be hints of a new

particle like the elusive gravi-ton or a heavier cousin of the

Higgs Boson. It could also be a statistical fluke.

•BLAZAR BONANZA

Ground-based telescopes and NASA’s Fermi Gamma-ray

Space Telescope saw a blast of high-energy radiation stream-ing from a supermassive black hole half the universe away —

a surprise because the extreme energy is traveling

such a long distance.

•COMET DANGER

Giant comets pose more dan-ger to life on Earth than aster-oids, concludes a new study

that considers the hundreds of recently discovered Centaurs

beyond Jupiter. Each one holds more mass than all known asteroids crossing

Earth’s orbit.

•YOUNG GIANTS

The ALMA telescope in Chile spotted gaps in dusty disks

around four young stars. Astronomers suspect four giant planets carved the

paths.

•CLUMPY DOUGHNUTS

NASA’s NuSTAR space telescope looked at one of the largest

known doughnut-shaped disks feeding a supermassive black hole, NGC 1068 in the constel-

lation Cetus, and found the material is clumpy, and not uni-

form as once suspected.

•STOLEN STRUCTUREA study of seven planetary nebulae in the Andromeda Galaxy’s Northern Spur and Giant Stream regions shows that the two substructures

share a common origin, form-ing as our neighbor interacted with one of its satellites, M32.

•BRAVE NEW WORLDS

Quijote, Brahe, and Lipperhey are among the dozens of

names announced for newly found exoplanets and their

host stars in an online public vote held by the International Astronomical Union. The alien

worlds received more than half a million votes from some 182 countries and

territories. — E. B.

NEAREST NEIGHBORS. Astronomers have found a super-Earth orbiting the star Wolf 1061, which sits just 14 light-years away. If confirmed, the world would be the closest potentially habitable planet known.

Rocky discoveries on Mount Sharp are puzzling

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ROCK ON. NASA’s Curiosity rover has discovered silica-rich rocks in the Marias Pass region of Mars’ Mount Sharp. In this view of the pass, the lighter area at center is an older section that abuts an overlying layer of sandstone. NASA/JPL-CALTECH/MSSS

STELLAR SHOCK. Every star eventually exhausts its fuel, but only large stars implode after using up their thermo-nuclear supply. Then their outer layers collapse on the newly formed neutron star and shoot back out as a supernova explo-sion. Sometime within the past 30,000 years, this process created the Jellyfish Nebula and what scientists think is a rapidly spinning neutron star, or pulsar, at its southern edge known as J0617. This composite image (inset) combines new Chandra X-ray Observatory data (shown in blue), with Sloan Digital Sky Survey imagery (all other colors) to show that a circular structure (faint blue) surrounds the pulsar, which also shoots out a large jetlike feature. Scientists say the ring could be a sign that high-speed winds were shot out and then slowed abruptly; or the ring might be like a shock wave sprinting out ahead. — Eric Betz


The scene is the

Huntsville, Alabama,

airport, circa 1978.

Two astronomers

are talking, wait-

ing for their plane. They were

at a meeting of the recently

formed Space Telescope Science

Working Group, hashing out

details of what will one day be

called Hubble. As conversation

goes from topic to topic, they

wonder what you could do if you

pointed an orbiting 2.4-meter

telescope down instead of up.

Both are future winners of

MacArthur Foundation “genius

grants.” One is Jim Gunn, a

brilliant cosmologist known for

his contributions to our under-

standing of the early universe,

and for his penchant for rebuild-

ing instruments during the day

while observing at night.

The other man is the recently

named principal investigator

of the space telescope’s premier

instrument, the Wide Field/

Planetary Camera (WF/PC).

Widely regarded a genius at

instrumentation, Jim Westphal

was among the first to put a

bolometer on a telescope to

look at the infrared sky. More

recently, he put a new kind of

detector, a CCD, into a vacuum

flask made from a spaghetti

pot and put it at prime focus on

the 200-inch Hale Telescope on

Palomar Mountain.

A full professor at the

California Institute of

Technology, Westphal seems

an obvious choice to hold the

future of astronomy in his

hands. Obvious, that is, were it

not for the fact that by formal

training he is a petroleum geo-

physicist with only a bachelor’s

FORYOURCONSIDERATION B Y J E F F H E S T E R

Puckish

brilliance Jim Westphal had an uncommon mind.

in physics from the University

of Tulsa. With his flattop hair-

cut, beard, and flannel shirt, he

might look more at home in an

oil field, and the skillful ways he

turns the air blue would make

any roughneck proud.

The two Jims go to work

on the back of a napkin. They

calculate a down-looking tele-

scope’s resolution, consider

data rates, decide how best to

use existing imaging technol-

ogy, estimate the rate of ground

coverage, and on down the line.

The questions aren’t hard, but

they are undeniably fun.

Fast-forward several weeks.

Westphal is in Palo Alto,

California, when a high-ranking

Lockheed executive invites him

to lunch. Sitting in the execu-

tive dining room, Westphal’s

host suddenly becomes serious.

“Westphal, you are too smart

for your own damned good!

And watch what you say when

you are sitting in airports!”

It seems the earlier conver-

sation was overheard and was

creating a stir among people

worried about security leaks. It

troubled them that a couple of

civilians could deduce the exis-

tence of the Keyhole KH-11 spy

satellite and correctly describe

its capabilities, all during a few

minutes of casual conversation.

I met Westphal some years

later when he hired me to work

with the WF/PC team. Jim was

a storyteller, and the time he got

the spies worried was a story he

loved to retell. It said a lot about

who he was.

Jim reveled in the very idea of

physics. You can’t hide physics,

and you certainly can’t hide from

it. In a debate between physics

and politics, physics wins. Every

single time. I think it confused

him that anyone could ever for-

get such an obvious and funda-

mental fact. But he knew it when

they did! The man could smell

manure a mile away.

Whether sitting at a telescope

or lowering a camera into Old

Faithful (yes, really), Westphal

took an almost childlike joy in

the world. His highest praise

was to call something “really

neat.” He heralded good news by

exclaiming, “Science and engi-

neering triumphing over igno-

rance and superstition!” That

enthusiasm was contagious.

I recall a night in Hawaii

when he led the entire WF/PC

science team out onto recently

cooled lava — “Look at the red

glow coming from the crack

under your feet!” — to watch

molten rock pour into the

ocean. He knew it was against

the rules, but since the rangers

left at sundown, he also knew

that no one would stop us.

Ask Westphal for advice,

and nine times out of 10 he

would say, “If you aren’t having

fun, you aren’t doing it right!”

Jim didn’t care much about

hierarchy. He did care about

competence, and he earned the

fierce devotion of the people

who worked with and for him.

I recall someone asking him

how he assembled such a tal-

ented group and coaxed them

into doing such remarkable

things. Managers could learn a

lot from his answer: “You find

really clever people. You pro-

vide them with resources. You

protect them from nonsense.

And then you get the hell out

of their way!”

I owe Jim Westphal my

career. More than that, I owe

him my understanding of what

intellectual integrity looks like.

Jim didn’t live to see

Hubble’s 25th anniversary. He

died in September 2004. I don’t

know that I heard his name

mentioned during any of last

year’s official Hubble com-

memorations.

But those of us who were

there know that he is a huge

part of Hubble’s soul.

BROWSE THE “FOR YOUR CONSIDERATION” ARCHIVE AT www.Astronomy.com/Hester.

Jim Westphal and his son, Andrew, now a physicist at the University of California, Berkeley, wait for the launch of the Hubble Space Telescope with STS-31. JEFF HESTER

Jeff Hester is a keynote speaker, coach, and astrophysicist.

Follow his thoughts at jeff-hester.com.

NASA’s New Horizons spacecraft continues to send data back from its

Pluto flyby last July. At year’s end, more than half the data remained on the

spacecraft, waiting to be sent back to the eager eyes of scientists and the

public. The highest-resolution data reveal complicated geology and myste-

rious terrain, and Pluto’s active ice surface is still delivering surprises. — K. H.

ZOOMING IN ON PLUTO

STEPPING

ACROSS

The zigzag images here are due to New Horizons’ imaging camera acting in “ride-along” mode with its spectrometer. The pair of instru-ments sampled terrain from the far west of New Horizons’ view of Pluto to the day-night line known as the terminator, skirting the dark Cthulhu Regio along the way. NASA/JHUAPL/SWRI

PLUTO’S PITS.

Across Pluto’s heart-shaped region known as Tombaugh Regio, new high-resolution images (this region is 50-by-50 miles or 80-by-80 kilometers) reveal a complicated system of pits. Ice fracturing and evapo-ration is probably responsible for the many tiny indenta-tions. NASA/JHUAPL/SWRI

NOW IN COLOR.

NASA’s New Horizons spacecraft caught its sharpest views of Pluto from a distance of only 10,000 miles (17,000 kilometers), yielding black and white views with a scale of only 280 feet (85 meters) per pixel, with the color-image overlays less resolved, roughly 2,000 feet (630m) per pixel. NASA/JHUAPL/SWRI

ASTRONEWS


ASTROCONFIDENTIAL B Y E R I C B E T Z

When NASA takes off for Europa in 2022, humanity can thank this lifelong space enthusiast from the Houston suburbs.

John Culberson got his first

telescope at age 12. It was 1968,

and humanity was headed to

the Moon. Growing up in the

Houston suburbs, he saw those

Apollo astronauts as heroes. Flat

feet and bad vision pushed him

into a career in public service

instead, but he never turned away

from his love of astronomy.

Then, in 2014, Culberson

finally got the job in Congress

he’d wanted for more than a

decade. He was selected chair of

the Commerce, Science and

Justice appropriations subcom-

mittee, which controls the budget

for, among other things, NASA

and the National Science

Foundation. His goal is to restore

NASA to its Apollo glory days.

And he’s just getting started.

Culberson wants NASA to go to

Europa to find alien life. When

they do, he says, it will be a cata-

lyzing moment for humanity that

will boost NASA budgets to the

level necessary to begin planning

for the next step: interstellar

travel. Astronomy caught up with

Culberson in early January after

the omnibus spending bill passed.

Q: Why Europa? What’s

driving your interest

in these ocean worlds?

A: I believe the good Lord has

seeded life all around us as far as

the eye can see, and I am con-

vinced that we will find life on

another world for the first time

in our own backyard. Odds are

that will end up being in the

oceans of Europa. That’s the con-

sensus of the planetary science

community — of the best minds

in the space program. They all

agree that the one place in our

solar system where all the condi-

tions are present for life to have

evolved safely and securely, and

in an environment that has all

the right ingredients, is in the

oceans of Europa.

Q: NASA didn’t want a lander

on this mission, but would it

be disappointing if we went

there and didn’t look for life?

A: Absolutely. You cannot answer

the question “Is there life on

other worlds?” without landing

on the surface and testing and

tasting the ice and the plumes

that are undoubtedly

there. There’s no other

way to know if there’s

organic molecules there

— if there’s life in that

ocean — unless you land on

the surface. That’s the con-

sensus of the scientific commu-

nity. I’m convinced they’re right.

And you know, since NASA’s a

big bureaucracy, it’s difficult to

get them to move or do things,

so it was necessary for me to

write it into law. In fact, this

Europa mission with a lander is

the only mission that it is illegal

for NASA not to fly. And I made

certain of that.

Q: What would finding life

there do for humanity?

A: When that happens — when

life is discovered on another

world — that will be remem-

bered forever as a transforma-

tional moment in human history.

And it will galvanize the human

race and the people of the United

States to support our space pro-

gram to the extent that’s neces-

sary to take NASA to the next

level. That will allow us to

develop for the longer term the

first interstellar rocket propul-

sion to take the first mission to

Alpha Centauri. I want to lay the

groundwork to see that happen. I

want to see us be able to make it

safe for humans to do very deep-

space long-range flights that pro-

tect the health of our astronauts

and allow them to do great sci-

ence. That’s going to require a

massive investment in new tech-

nology to shield the astronauts

from coronal mass ejections and

the constant threat of cosmic

radiation. And that can be done,

but NASA’s not making those

investments.

THE EUROPA MANDATE. U.S. Rep. John Culberson (R-Texas) poses with members of NASA’s Europa mission team. The congressman gets regular mission updates in meetings with engineers and scientists. COURTESY JOHN CULBERSON

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Q&A with Texas Rep. John Culberson

“This Europa mission with a lander is the only mission that it is illegal for NASA not to fly. And I made certain of that.”

Read about the new Europa mission on page 22.

ASTRONEWS

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FAST FACT


COSMIC KITCHEN. An Italian linear accelerator has seen the first nucle-ar reaction creating sodium in a red giant star similar to our future Sun.

Astronomers using the world’s most sensitive radio telescope have discovered a “nest” of infant galaxies lying some 11.5 billion light-years away. Lots of very young and very distant galax-ies are known; what makes these special is that they’re clustered within a web of dark matter, wrapped within a junction of giant filaments. Moreover, they are monstrous galaxies with star formation rates hundreds or thousands of times greater than the galaxies we observe closer to us in the present-day universe.

Ideas about the formation of galaxies in the early universe suggest that such galaxies should form in special environments where dark matter is concentrated. Without the incredible power of ALMA, the Atacama Large Millimeter/submilli-meter Array, however, the search for these kinds

of young galaxies was incredibly difficult. Now astronomers using this high-altitude radio tele-scope in Chile have peered through obscuring dust to reveal them.

The research team led by Hideki Umehata, Yoichi Tamura, and Kotaro Kohno of the European Southern Observatory and University of Tokyo observed a tiny part of the sky in the constellation Aquarius, uncovering these galax-ies in a region designated SSA22.

The data from ALMA allowed the researchers to pinpoint the locations of nine monstrous gal-axies within a small group tucked inside a “great wall” of dark matter filaments. The discovery will shed light on galaxy formation, and opens up the possibility of finding other, similar groups of powerful, infant galaxies. — David J. Eicher

ALMA spots monstrous infant galaxies

MERCURY IN THE EVENING

GALACTIC COCOON. Astronomers using the ALMA radio telescope in Chile have uncovered a “nest” of huge infant galaxies born within a weblike structure shown in this visualization, some 11.5 billion light-years away.

SHY PLANET. Mercury has a reputation for being difficult to see because it typically hugs the horizon during twilight either after sunset or before sunrise. The chart plots the innermost planet’s positions 45 minutes after sunset for observers at both 35° north and south latitudes for the planet’s three evening elongations in 2016 (except for its April Southern Hemisphere appearance, when it appears less than 1° high). Note that Mercury’s peak altitude often doesn’t coincide with its greatest solar elongation (dates highlighted in white). ASTRONOMY: RICHARD TALCOTT AND ROEN KELLY

From 35° north latitude, Mercury peaks at an

altitude of 10.0° April 18; from 35° south, the

planet climbs 17.2° high August 17.

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Two hundred and

twenty-five years ago,

Benjamin Banneker,

a self-taught astrono-

mer and mathemati-

cian from Baltimore County,

Maryland, helped survey the

boundaries of our nation’s

capital using the stars as guides.

Over the years, a rash of books

has flavored this episode in

American history with sprinkles

of the occult, including sacred

alignments of key structures

with bright stars. But critics

have picked apart many of these

claims like crows on roadkill.

Indeed, American historian

Silvio Bedini, who wrote the

definitive biography of Bann-

eker, notes that “considerable

confusion” exists among writ-

ers concerning Banneker’s role

in the survey of our federal city.

Nevertheless, we can still look

to the stars this month and

SECRETSKY

Three ‘capital’ stars? Did the positions of bright stars

have anything to do with the layout of Washington, D. C.?

Exposure to inclement

weather, especially the cold,

took its toll on 60-year-old

Banneker, who often would stay

up all night, making observa-

tions — until he fell ill and

returned home probably in late

April 1791.

Triple threatA parade of bright stars crossed

the south meridian during

Banneker’s stay, including

Regulus (Alpha [α] Leonis),

Spica (Alpha Virginis), and

Arcturus (Alpha Boötis).

According to David Ovason,

author of Lost Symbols? The

Secrets of Washington DC,

this seems “to reflect the cen-

tral triangle in the plan of

Washington, D.C.” (the Capitol

Building, the White House, and

the Washington Monument).

Alas, none of these stars

passes directly over the city at

any time, and not any of

Ovason’s suggested celestial

and terrestrial triangles match

up upon projection. Still, peo-

ple wonder if Banneker saw

these three stars as fitting sym-

bols of our nation’s capital.

Could anything have fueled his

imagination?

Capital triangle?Nicolas Copernicus named

Regulus (the Little King) from

the belief that it “ruled the

affairs of the heavens” — a fit-

ting symbol, as our nation’s

B Y S T E P H E N J A M E S O ’ M E A R A

government has political

authority to rule over the

actions and affairs of the

people. Regulus also leads

Arcturus and Spica across the

heavens. Arcturus (the Bear’s

Guard) escorts the Great Bear

around the North Celestial

Pole. This might symbolize the

flow of cosmic justice through-

out the night, just as our

government keeps watch over

its flock and reigns supremely

over any injustice. And finally,

there’s Spica (Ear of Grain),

a just symbol of our nation’s

health (amber waves of grain).

Banneker’s attention could

have been drawn to this trio of

stars by Jupiter, which lay about

midway along a line between

Regulus and Spica in Virgo,

whom we see in a classical

dress holding an ear of grain. I

mention the description of

Virgo because the original

design of the Statue of Freedom

atop the Capitol Building was a

female in a classical dress hold-

ing an ear of wheat.

So rather than trying to

force stars onto Earth, all one

has to do this month is look

east around 9 p.m. and see the

three capital stars that Bann-

eker must have seen (if not

measured and identified) in his

nightly transit surveys of our

nation’s capital.

As always send all of your

thoughts to sjomeara31@gmail.

com.

imagine something “capital”

about them.

Banneker’s roleBanneker’s assignment was to

assist Maj. Andrew Ellicott,

whom President George

Washington appointed as

the head of a six-man team.

First observations com-

menced February 11, 1791, and

Banneker was the principal

observer. Ellicott tasked him

mainly with determining the

starting point of the survey

and maintaining a clock that

could relate points on the

ground to the positions of the

stars at specified times.

Banneker made observations

of “about a half-dozen different

stars crossing the meridian at

different times during the

night, and the observations

were repeated a number of

times,” Bedini says.

BROWSE THE “SECRET SKY” ARCHIVE AT www.Astronomy.com/OMeara.

Did the stars Regulus, Spica, and Arcturus inspire Benjamin Banneker to envision a layout for Washington, D.C.? JOHN CHUMACK

Regulus

Arcturus Spica

FROM OUR INBOX

No opinions, just science, pleaseNot long ago, I stopped home delivery of my local newspaper.

It had become so politically biased that I came to see I was not

getting objective news. I hope I’m not seeing the beginning of

the same kind of bias in my favorite magazine.

In the November 2015 issue, editor David Eicher in his

“From the Editor” column presents issues that many consider

politically sensitive. The suitability of GMOs, global warming,

and the validity of vaccine use are listed. He decries those who

hold opinions opposite his as people who wage what National

Geographic calls “The War on Science.”

Don’t get me wrong. Editor Eicher may be correct on all

these issues. My objection is in his bringing these political mat-

ters into Astronomy magazine and even taking a side. Doing so

negatively changes the magazine’s atmosphere. In short, dump

the political stuff and stick solely with science.

— George Dreitlein, Little Falls, New Jersey

ASTRONEWS

Earth

Sun

Observer at another starAngle =

1 arcsecond

Distance = 1 parsec

Stellar cannibalism

Stellar collision

Blue Stragglerstar


FAST FACT

NASA got an unexpected gift from Congress to close out the 2015 holi-day season: a significant increase in funding. The 2016 omnibus spend-ing bill is the most generous in years. It allocates $19.3 billion to NASA. Previous versions of the bill included cuts for some programs, but those were almost completely reversed in the final version approved by the House and Senate. NASA’s Planetary Science program picked

up a 13 percent increase to $1.63 billion, and the space agency’s overall science budget increased by 6.6 percent to $5.6 billion. Even Earth science saw an increase of 8.4 percent after much noise about cuts earlier in the year. The new budget includes $175 million for a mission to Europa and mandates the mission carry a lander as well, something NASA didn’t want on the current mission. — E. B.

Big boost for science in latest NASA budget

WHAT’S A PARSEC?

LIFE EXPLODED. In a first, scientists have shown that oxygen levels on Earth rose slowly for 100 million years in drawn-out fits and starts before reaching the level that allowed life to explode about 600 million years ago.

Lightsaber star

Astrobabble From asterisms to Thorne-Żytkow objects,

we turn gibberish into English.

Cos·mo·drome from the Greek drómos, or race track A Russian launch site, like the $13.9 billion Vostochny Cosmo-drome being prepped for Soyuz spacecraft in that country’s far east. Vladimir Putin wants a new spaceport following disputes with Kazakhstan, the current launch host.

Hex·a·hy·drite A type of magnesium sulfate — like the soothing salts you drop in a hot bath — with six water mole-cules that forms flaky, fibrous lay-ers and is now thought to explain the strange bright spots in Occator Crater on the asteroid Ceres.

Blue Strag·gler >>The result of stellar cannibalism or a collision that turns two old red stars into one massive, hot blue star that looks like it’s lagged in its evolution. These brilliant stars confuse astrono-mers by finding the fountain of youth in otherwise ancient glob-ular clusters.

Yar·kov·sky ef·fect Caused when photons from the Sun hit a spinning rock (typically meteoroids and small asteroids) and are re-emitted as heat in a random direction, ever so slightly changing the space rock’s path. — Eric Betz, [email protected]

A parsec corresponds to

exactly 648,000/π astronomical units (AU; the

average Earth-Sun distance).

A UNIT OF DISTANCE. Ignore Han Solo’s Kessel run. A parsec is an astronomical unit of distance based on geometry. Also equal to 3.26 light-years, it represents how far away an observer would be to observe the Earth and Sun separated by 1 arcsecond on the sky. By flipping the system around, astronomers can measure distances to stars by parallax, or how much they appear to move as the Earth travels around the Sun. ASTRONOMY: ROEN KELLY AND KOREY HAYNES

THE FORCE AWAKENS. In the Orion B molecular cloud complex, a young star is still gathering the material that will one day make up its bulk. It shoots out jets of excess gas from its poles, forming a bright beam reminiscent of a Star Wars lightsaber. The jets collide with surrounding clouds of material, pro-ducing shock waves and forming a nebulous region called a Herbig-Haro (HH) object. This protostar has formed HH 24, and astronomers are studying it care-fully to learn more about how stars form and grow. — K. H.

ESA

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SIT

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For more on the Yarkovsky effect see page 28.


It’s April, and that means

another baseball season

is underway. To celebrate,

let’s take a field trip to a

pair of diamonds. No, we

won’t be running the base paths

at Wrigley Field or Yankee

Stadium. Our diamonds are of

the cosmic variety, and both lie

in the constellation Virgo.

The first is a huge naked-eye

asterism (a recognized star pat-

tern that’s not a constellation)

first suggested by astronomy

popularizer (and Curious

George author) Hans A. Rey. In

his 1952 book The Stars: A New

Way to See Them, Rey intro-

duced readers to the “Virgin’s

Diamond.” He created this

four-sided figure out of the

stars Arcturus (Alpha [α]

Boötis) as the eastern point,

Spica (Alpha Virginis) as the

southern point, Denebola (Beta

[β] Leonis) to the west, and Cor

Caroli (Alpha Canum Venat-

icorum) to the north. Like the

Summer Triangle, autumn’s

Great Square, and the Winter

Hexagon, the Virgin’s Diamond

(more commonly known as the

Virgo Diamond or the Great

Diamond) is a convenient

guidepost to identify the con-

stellations of spring.

We’ll revisit this stellar quar-

tet next month, looking at their

OBSERVINGBASICS B Y G L E N N C H A P L E

Play ball! It’s the season

for diamonds.

Astronomical Society, describ-

ing it as “a system of five stars,

containing objects of 12–13

mag and arranged in the form

of a diamond.” He surmised

the system was probably an

evaporating small cluster.

Because Brosch was the first on

the scene, some sources refer to

the stellar group as Brosch’s

Diamond.

News of the discovery

caught the attention of North

Carolina amateur Roger

Ivester, who viewed Brosch’s

Diamond on the night of April

14, 1993. Through a 10-inch

f/4.5 reflector at 190x, he saw a

faint grouping of four stars but

could not spot the fifth. Nine

years later, on an evening of

exceptional seeing conditions,

he finally caught a fleeting

glimpse of the elusive star with

the 10-inch scope and a magni-

fication of 266x.

One thing that really im-

pressed Ivester about Brosch’s

Diamond was its symmetry.

Each side is 33" to 37" long,

giving it the square appearance

of a baseball diamond. Home

plate is the magnitude 10.7 star

TYC 4948–53–1. Stars of mag-

nitudes 13.2, 13.2, and 12.3

represent first through third

base, respectively. Most chal-

lenging is the magnitude 13.7

fifth star, just 7" from third

base at a spot where the third

baseman would play. Ivester

has so vigorously promoted

Brosch’s Diamond that some

amateur astronomers call it

Ivester’s Diamond.

Last spring, I viewed the

Diamond with a 10-inch f/5

reflector. I star-hopped from

Zaniah (Eta [η] Virginis) using

60x and came upon something

tiny and fuzzy, not unlike the

four-star asterism that com-

prises M73. A boost to 208x

revealed the Diamond. Home

plate and third base were read-

ily visible; first and second

required averted vision. In a

rich Milky Way field, the Virgo

Diamond would have been lost,

but in this star-poor region of

Virgo, it stood out dramati-

cally. I couldn’t see the fifth

star, but I was observing under

turbulent skies with a 5th-

magnitude limit.

Questions or comments?

Email me at gchaple@hotmail.

com. In my next column, we’ll

time travel to the stars of

spring. Clear skies!

distances and those of other

prominent spring stars.

For now, let’s step outside for

a telescopic look at Cor Caroli,

a superb double star. We won’t

need a big, high-power tele-

scope. A 2.4-inch scope at just

50x will split the 19.3" that sep-

arate its components, which

shine at magnitudes 2.9 and

5.5. Sources disagree as to their

colors. The first time I saw Cor

Caroli, the stars seemed white

and bluish. On a more recent

occasion, the brighter star

looked a bit off-white. What

colors do you see?

The other Virgo Diamond

isn’t as readily seen as Rey’s. It’s

faint and surprisingly small,

composed of five stars of magni-

tudes 10.9 to 13.7, and squeezed

into an area small enough to be

covered by Jupiter when it lies at

opposition. To capture it, you’ll

need the finder chart on this

page and a medium-size tele-

scope (6 inches or larger) cou-

pled with an eyepiece that

magnifies at least 150x.

This diamond appears to

have been discovered by Noah

Brosch of the Tel Aviv Obs-

ervatory. Brosch spotted it on a

Palomar Observatory Sky

Survey plate. He reported it in

the December 1991 issue of

Monthly Notices of the Royal

FROM OUR INBOX

Correction

On p. 20 of our January 2016 issue, we mistakenly labeled

Alnitak as Delta (δ) Orionis. In fact, this star is Zeta (ζ)

Orionis. — Astronomy Editors

BROWSE THE “OBSERVING BASICS” ARCHIVE AT www.Astronomy.com/Chaple.

This magnified view of the Virgo Diamond shows a field of view 52' wide. The faintest stars shown are approximately magnitude 15.

The Virgo Diamond lies at approximate right ascension 12h33m and declination –0°39'. It is visible through a 10-inch telescope if your seeing (atmospheric steadiness) is good. This view shows a field 2°40' wide. BOTH IMAGES: SOFTWARE BISQUE: THESKY

We welcome your comments at Astronomy Letters, P. O. Box 1612,

Waukesha, WI 53187; or email to [email protected]. Please

include your name, city, state, and country. Letters may be edited for

space and clarity.

ASTRONEWS


Ever since NASA’s Dawn mission arrived at Ceres, one question has dominated discussion of the dwarf planet: What are those weird white spots? Some scientists suspected water ice, others thought it was clay, and many more suggested salt. Astronomers had turned to salt as the most likely explanation, but a new study published in Nature December 10 finally gets specific. The shiny substance is hydrated magnesium sulfate — Epsom salt — and it covers peaks and crater rims across Ceres.

The salt is mixed with water-ice mole-cules, making the bright spots stand out against the clay carbonates in the asphalt-colored surrounding surface. The biggest question now is how it gets there. The Dawn team counted more than 130 bright spots across the world’s surface, and most of them are associated with impact cra-ters. So, the most likely explanation is that space rocks impact Ceres’ surface and excavate briny water from the dwarf plan-et’s interior. The ice then sublimates, leav-ing the salt and creating the hazes that the Dawn team has watched in the region near the white spots. — E. B.

Dawn explains Ceres’ salt

CASSINI’S CLOSE-UP. NASA’s Cassini spacecraft had its final close encounter with Saturn’s moon Enceladus December 19, passing within 3,106 miles (4,999 kilometers) of the surface.

Planetary nebulae are the expanding shells of gas that a star like our Sun expels at the end of its life and then lights up with its white-hot core. They fade over tens of thousands of years — the blink of an eye in astronomical terms. Understanding these glowing beauties depends in part on understanding their size, which is inti-mately tied to their distance from Earth.

Astronomers published January 11 in Monthly Notices of the Royal Astronomical Society their updated method that uses a target’s apparent size on the sky, its brightness, and how much dust lies along the line of sight, potentially dim-ming the object. With this, researchers gain a fac-tor of five in how accurately they can pinpoint the object’s size and distance. — K. H.

Resized planetaries

A SALTY DWARF. In addition to the bright Occator Crater, NASA’s Dawn spacecraft has now spotted more than 130 additional white regions across Ceres’ surface. Almost all of these salty spots coincide with craters. NASA/JPL-CALTECH/UCLA/MPS/DLR/IDA

ACTUAL SIZE. A new measurement for planetary nebula PuWe 1 produces the scale shown at left. Older calculations (right) underestimate its true size and distance. NOAO/AURA/NSF/IVAN BOJICIC/DAVID FREW/QUENTIN PARKER (HKU)

4 ly

ScopeStuffTelescope Accessories & HardwareWorld’s largest inventory of telescope accessories,

adapters and hardware. Free shipping in the USA!

www.scopestuff.com512-259-9778


The life aquatic

he first dives to the dark and deep places of our planet revealed a moonscape. Beneath icy waters and far from the Sun’s nourishing light, the planet appeared dead. No plants. No photosynthesis. No photons.

But then scientists in submarines began exploring Earth’s single greatest mountain range, the Mid-Oceanic Ridge, which occupies almost a quarter of our world’s surface. Explorers like Robert Ballard call this great rift the Boundary of

Creation. Here, our planet bleeds molten blood through some 10,000 active volcanoes and then cools to heal itself.

In the mid-1970s, Ballard was among the first to see this other Earth. (In ’85 he discovered Titanic.) Along the Galapagos Rift, his team came across great white chimneys rising more than a dozen stories. Instead of a desert, they found thriving ecosystems in temperatures that would melt lead. No sunlight could reach such depths. But alien creatures abound in this abyss anyway. Great tube worms towered 10 feet tall alongside clams colonized by symbiotic bacteria.

And in decades of expeditions all over Earth, scientists con-tinue to turn up new forms of life that can replicate photosynthesis using only chemicals. Their energy source, their evolutionary ori-gins — even their food chain is distinct from ours.

These so-called extremophiles kindle hope that alien life is abun-dant and, just maybe, nearby. Liquid oceans have been found on Saturn’s moons Titan, Enceladus, and possibly Mimas, as well as Jupiter’s moons Europa, Ganymede, and Callisto. And scientists are investigating possible oceans on the dwarf worlds Pluto and Ceres.

But out of all these water worlds, Europa is still the most entic-ing. It packs more saltwater than Earth and shows signs of geo-logic activity, like underwater volcanoes and potential water vapor plumes spotted by the Hubble Space Telescope. Scientists also sus-pect the surface ice mixes with the water below, delivering the nutrients necessary for life.

If we find life in only one other place in our solar system, it most likely will swim in the seas of Europa, pulling chemical energy from hydrothermal vents. But the cost has remained too high for that draw to translate into an actual space mission — until now.

In just six short years, NASA will launch the first mission to explore Europa and possibly even land on it. After decades of false hopes and well-conceived missions that proved too expen-sive, the space agency has officially greenlighted a multibillion-dollar mission that could help answer the ultimate question: Are we alone in the cosmos? The Europa Multiple Flyby Mission isn’t the first one on the books, but it does appear to be the one that will make it.

“We’re all saying it looks like this one’s gonna stick,” says Europa mission Deputy Project Scientist Dave Senske of the Jet Propulsion Laboratory (JPL). “Everything’s moving in the right direction where we’ve got a lot of support from NASA, we’ve got support in Congress — the stars are aligning. It is Europa’s time.”

Liquid water on Europa?In 1977, the same year divers first explored Earth’s hydrothermal vents, two very different explorers of the deep launched on a path to the first reconnaissance of another ocean world — Europa.

Voyager 1 visited Saturn and Jupiter, where it watched as the moon Io let off a volcanic blast. And something strange was hap-pening on neighboring Europa. Long, linear cracks crisscrossed its surface. But the probe couldn’t get close enough to see what was happening. Thankfully, Voyager 2 was close on its heels.

And on July 9, 1979, at 8:04 a.m. Pacific Time, faint rays of sun-light that had bounced off Europa’s icy surface and met the pass-ing Voyager 2 spacecraft were received back on Earth. Those first images traveled half a billion kilometers to where Carl Sagan’s eye-balls were waiting, along with the rest of the mission team.

Inside the historicAfter decades of canceled missions and false starts,

NASA is finally headed for Carl Sagan’s dream destination. by Eric Betz

mission

T

Eric Betz is an associate editor of Astronomy. He’s on Twitter: @ericbetz.

EUROPAto

NASA’s Europa Multiple Flyby Mission will skim Jupiter’s ocean moon dozens of times, creating the first high-resolution map of the world. NASA/JPL-

CALTECH/SETI INSTITUTE (EUROPA); NASA/

JPL/SPACE SCIENCE INSTITUTE (JUPITER)


“At first glance, the world looks like nothing so much as the canal network Percival Lowell imagined to adorn Mars,” Sagan eventually wrote of the experience. He wondered if the lines could be ridges or troughs, perhaps as a result of expansion and contraction. Could they have something in common with Earth’s plate tectonics?

“At the moment of discovery, the vaunted technology has pro-duced something astonishing,” Sagan wrote. “But it remains for another device, the human brain, to figure it out.”

In reality, the puzzle had been solved before Voyager even arrived. Three astronomers — Stanton Peale, Patrick Cassen, and Ray Reynolds — published a paper in the journal Science just before the Jupiter flyby suggesting volcanism on Io. The trio rea-soned that the moon always made its closest approach to Europa at the same spot in its orbit. This resonance creates an orbital eccen-tricity just big enough for a tidal pull from the hefty nearby gas giant. The approach also makes Io’s volcanoes spew sulfur on Europa’s surface — potentially a key factor for any life under the ice.

And, if the tugs from Jupiter could heat Io, they could cause volcanism on Europa too. Those aqueous allusions have grown into a widespread assumption that a global ocean lurks beneath many miles of ice. On the cover of the October 1979 Geophysical Research Letters, the same three astronomers also published a paper titled “Is there liquid water on Europa?” It’s a question that still needs a solid answer.

Galileo’s tantalizing findsAlmost all knowledge of Europa comes from a limited data set gathered by NASA’s Galileo mission to the Jupiter system. Launched in 1989 after years of delay due to the space shuttle Challenger disaster, Galileo rewrote planetary science textbooks despite being plagued by one severe problem. The spacecraft’s 16-foot-wide umbrella-shaped high-gain antenna was supposed to unfurl after traveling far enough from the Sun. This would allow large images to be sent back every minute for years. Instead, the motor got stuck, and the antenna never raised.

Galileo’s inadequate connection turned a data deluge into a trickle. Observations were forced through a secondary dish using a signal 10,000 times fainter. With only a dozen close flybys of Europa (the spacecraft went into safe mode on two of those), JPL scientists had to make the most of their opportunities. The single highest-resolution Europa image ever taken has just 6 meters per pixel resolution and isn’t even in color.

Still, Europa’s first photo album was startling. Galileo imagery seemed to confirm what astronomers suspected: Europa was best explained as a spinning shell of ice atop a large liquid water ocean. The surface also gave clues to Europa’s history. Its fractured and icy terrain crawls around, breaking up and pushing together in a pro-cess akin to plate tectonics — the only known world other than Earth with such geology (See “Ice tectonics,” p. 25).

Galileo’s magnetometer also detected an induced magnetic field between Jupiter and Europa. The easiest way to interpret that is with a salty, global subsurface ocean. Ice simply isn’t conductive enough.

The team only managed to gather enough data for a frustrat-ingly low-resolution map of the moon, but the few high-resolution images were enough to whet scientists’ appetites. Many of the cur-rent small crop of Europa scientists worked as graduate students using Galileo data. To them, a follow-up mission seemed obvious. But in the years since Galileo’s 1995 arrival at Jupiter, scientists watched NASA launch 11 missions to Mars without a single craft to explore Europa.

The mother of innovationEuropa mission Project Scientist Robert Pappalardo is among those scientists in waiting. He figured his work on Galileo would lead to a job on an eventual Europa trip. And, around the turn of the mil-lennium, that dream looked likely to come true when a group of astronomers proposed the Europa Ocean Discovery mission.

Hubble caught water vapor plumes escaping from Europa’s south pole, shown here in an artist illustration using real images but enhanced ejecta.

In 2013, a team of scientists on the British research vessel James Cook used remote controlled submersibles to explore hydrothermal vents 16,400 feet (5,000 meters) below the ocean surface. They found blind shrimp and abun-dant anemones. NATIONAL OCEANOGRAPHY CENTRE

NA

SA

/ES

A/A

ND

M.

KO

RN

ME

SS

ER

Cold, brittle outer ice shell

Warmer, convecting portion of ice shell

Liquid ocean

Subducting plate denser than deeper, warmer ice

Subsumption of plate into shell interior

Cryolavas

Truncated older features

Subsumption band


Ultimately, the small craft was seen as unrealistic and NASA moved in favor of New Horizons’ trip to Pluto instead. Still, the decadal survey, a document summarizing the planetary science community’s priorities, ranked Europa near the top. Astronomers wanted a Europa orbiter.

Eventually the space agency asked Pappalardo and a team of JPL scientists for an intermediate-class mission. The team com-bined efforts with the European Space Agency’s mission to explore Jupiter’s other icy moon, Ganymede. They called it the Jupiter Icy Moon Explorer — JUICE. This time, the astronomical community said the concept wasn’t worth the cost. NASA backed out, leaving the Europeans to build JUICE themselves. (That mission is planned to launch in 2022.) “I said I’ll go to JPL and if after three years you don’t get a mission, I’ll go back to academics,” Pappalardo says. He didn’t give up. “After nine years, I’m still here. It was a little like Lucy and the football.”

The complicating factor in all these missions was that Europa’s orbit sits some 400,000 miles (644,000km) from our solar system’s biggest planet. That’s about twice as far away as the Moon is from Earth. Any spacecraft needs heavy radiation shielding to with-stand the deadly downpour of high-energy electrons streaming off Jupiter at nearly light speed.

After the latest orbiter was rejected, NASA asked its scientists to look at alternatives, and they found several. One plan seized on something genius NASA had already mastered: studying the moons of Saturn. JPL’s Brent Buffington worked miracles calculating the extended Cassini mission trajectory. Buffington’s colleagues com-pare the crackshot astrodynamicist to Rich Purnell, the “steely eyed missile man” who saves the day in Andy Weir’s The Martian. Thanks to Buffington’s calculations, Cassini’s last seven years use the remaining 20 percent of fuel for 155 orbits that swoop by Saturn’s moons in daredevil flybys, finding signs of hydrothermal vents on Enceladus, rainfall on Titan, and other new science. During its clos-est flybys, Cassini scrapes within 16 miles (25km) of the surface.

Buffington was asked for the same magic as mission designer for a Europa flyby spacecraft. He divided the moon into 14 overlapping regions that allow a global map in high resolution. The best images will match those streaming from orbiters at Mars or the Moon. And, because it doesn’t stay close to Jupiter like a Europa orbiter would, the flyby design doesn’t require intensive shielding.

“We have an architecture that is much better tuned for a mis-sion of discovery,” says Europa mission Project Manager Barry Goldstein. “By having a mission where we loop in and out of the regime, we’re able to observe Europa from afar, and if we see a plume while we’re far out, we can adjust our flyby.”

If the moon has active plumes like the ones Hubble tentatively detected, the spacecraft could taste Europa’s ocean and determine its composition thanks to targeted flybys. The final proposal includes at least 45 flybys — radiation eventually will kill the spacecraft — almost all of which come within 60 miles (100km) of the surface. And it pulls it off for a low $2 billion. That’s half the expected cost of prior designs.

The combination of imagery and topographical data will revolu-tionize Europa science like the first 3-D data from the Moon and Mars did, says Europa Imaging System Principal Investigator Elizabeth Turtle of Johns Hopkins University’s Applied Physics Lab. But getting the photos isn’t easy. Inner solar system images benefit from the Sun’s brightness, as well as steady orbits around their less hostile targets. The Europa flyby mission’s closest passes will skim the surface at a height equal to Earth’s best spy planes. The ground below will move fast under extremely low-light conditions.

So, instead of borrowing technology from Cassini, whose CCD cameras have been challenged by similar conditions at Saturn, Turtle’s team turned to New Horizons’ LORRI camera. Its high-resolution flyby images of far-off Pluto have stunned the public over the past year. Instead of a CCD camera, the spacecraft uses CMOS, a detector that works better in low-light conditions.

“It’s a kind of detector that’s in a lot of digital cameras these days,” Turtle says. “It’s good for Europa because it’s more radiation tolerant than CCDs and it can do a much more rapid readout.”

The briny deepLike his colleagues, Kevin Hand also learned Europa while work-ing on images from Galileo. But the data-starved years since then have driven NASA’s deputy chief scientist for solar system explora-tion to extremes in search of new discoveries.

He trekked Alaska’s North Slope and explored Antarctica’s dry valleys. He also dove to the Mid-Atlantic Ridge and East Pacific Rise with Hollywood filmmaker James Cameron. There, he explored the Lost City Hydrothermal Field, which spews methane and hydrogen into the saltwater in a process much different from the black smok-ers found by Ballard and other explorers in the 1970s.

In 2014, scientists treated Europa’s crust like a jigsaw puzzle. They broke the surface into many pieces and then fit them back together. But a chunk the size of Wales was missing, implying plate tectonics (shown above) pushed it under the surface like Earth’s subducting plates. ASTRONOMY: ROEN KELLY, AFTER NASA/NOAH KROESE, I.NK

Europa’s fractured crust shows clear signs of a young surface — one that’s per-haps still actively shifting. This high-resolution mosaic of the Conamara Chaos region is one of the few such close-ups gathered by Galileo in the 1990s.

Ice tectonics

NA

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/JP

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There are no tube worms or clams. Instead, vastly different life-forms persist like snails, mollusks, and crustaceans. Many scientists believe similar sites served as the starting point for all life on Earth.

“Obviously, NASA’s mantra has long been ‘follow the water,’” Hand says of the space agency’s search for life. “We think [Europa] is where the water is.” But life requires more than that. It also needs energy. And it needs the elements to form life. Those things can come from volcanism recycling Europa’s rocky seafloor. However, for life to be widespread on Europa, vents aren’t enough. The life-forms Hand saw at Lost City are actually dependent on oxygen dissolved in the water. On Earth, that oxygen is derived from living things that use the Sun. Hand wanted to know if there was another way to get that oxygen on Europa.

He and his colleagues at JPL created what they call “Europa in a can.” The laboratory experiment allows the astronomers to repli-cate Europa’s temperature, pressure, and radiation conditions on tiny ice samples. The Galileo spacecraft saw hydrogen peroxide (H

2O

2) in just one place on Europa’s surface. So the scientists

showed in the lab how the chemical could form on the icy moon and eventually decay to oxygen (O

2). Finally, they used the twin

W.M. Keck Observatory telescopes in Hawaii to map the moon’s hydrogen peroxide deposits. Hand’s group also examined the strange colors that stand out on Europa’s cracked surface. They showed the browning yellow streaks are actually a byproduct of what happens when salt is hit by Jupiter’s radiation. “I think part of the discoloration we see on Europa’s surface is damaged sea salt,” Hand says, implying ocean water reaches the surface.

Hunting the white whaleMike Brown is perhaps better known as “Pluto Killer” for finding the new worlds that led to the dwarf planet’s demotion. He and Hand teamed up on the Europa salt studies. The pair found ways to use the massive Keck telescopes to gather observations with bet-ter resolution than even the Galileo spacecraft.

Brown likes to joke that they’re looking for Europa’s whales. And, in October 2015, one of his students netted Moby Dick.

This white whale leapt out when Caltech graduate student Patrick Fischer turned innovative mathematical formulas loose on the Keck observations. Fischer asked his computer to search an arbitrary collection of spectra for any strange signatures and then clump them into sets. Those were turned into maps. To his sur-prise, one of them perfectly mapped Europa’s bizarre chaos terrain — a result that shows it’s actually chemically different from the rest of the moon. What exactly is unique about the chemical fin-gerprint remains unknown. The team suspects that salt was recently cycled onto the surface there due to ice melt.

On our planet, this would be like a salt flat in the deserts of the American Southwest. On Europa, these salts are likely interacting with rocks at the seafloor. Sampling the deposits could give astronomers a way to reach deep beneath the ice and see the pro-cesses below. Western Powys Regio turned out to be the brightest such region, making it a prime place to land and look around. This newfound knowledge has helped a group of scientists push NASA to take a second look at sending a lander on the current Europa mission. Another force for a lander is U.S. Rep. John Culberson (R-Texas). He’s flooding the mission with cash.

A lobbyist for the outer solar system As a member of the Commerce, Science, and Justice subcommit-tee in charge of NASA funding, Culberson says he watched as the current and previous presidential administrations refused to give

the agency the funding it needs to complete all its missions. So, when he took over as committee chairman in 2014, the congress-man made sure funds for a Europa mission were written into law. He also holds regular meetings with the mission scientists and engineers to understand what they need in order to answer what Culberson calls “the most fundamental question we face.”

That last component, finding life on Europa, has also caused conflict within NASA. The space agency wasn’t planning to include a lander on this mission. But Culberson, who now controls the purse strings, forced the issue. To do the Europa mission right, he argues, scientists must be able to directly detect life. So he funded a JPL study to examine the feasibility of attaching a lander to the current flyby mission.

Culberson got Congress to set aside $175 million this year for developing both a flyby spacecraft and a lander. Congress also des-ignated money for the two prior years — before the White House even gave the mission an official spot on its own budget. That helped NASA move its spacecraft from pre-project to a formal proj-ect in 2015. And instruments were announced in May.

But Culberson’s hands-on approach has made him as much an opponent as an ally in the eyes of NASA headquarters. The Texas conservative is outspoken in his criticism of what he sees as a bogged-down big-government bureaucracy. But he was also the lead-ing force behind a recent 13 percent increase in NASA’s Planetary Science budget. And he’s trying to give NASA administrators longer terms that aren’t as dependent on the whims of the White House. But in the meantime, to make sure NASA spends the money on Europa as intended, the latest spending bill makes it illegal for NASA not to send along a lander. Culberson also mandated that the mission fly on NASA’s titanic Space Launch System (SLS), and that the launch take place by 2022 — the earliest opportunity.

“SLS is essential because it has the payload lift capacity to take


these complex, very large spacecraft out to deep space in record time,” Culberson told Astronomy in a recent interview. “The engi-neers tell me that they can achieve those goals.”

SLS is often decried for its high cost as a “rocket to nowhere,” but a less capable launch vehicle like the Atlas V would take more than six years to reach Europa, and most mission scientists will be near or past retirement age by the time it arrives. “As a team, we love the idea of flying on SLS,” says Goldstein, the project manager.

The Daniel Boone missionPart of the newfound push is that, absent a lander, the Europa mission can’t answer the question astronomers and the public most want answered. “From orbit and flybys, you can assess habit-ability, but to make a complete or convincing case for detecting signs of life, you really need to go down to the surface,” says Hand, who’s in charge of examining science from the lander. However, the flyby mission only succeeded because of its innovative and low-cost approach. NASA is cautious about adding a lander that could possibly cost another $1 billion.

“We’ve been the beneficiary of a significant amount of funding from Congress, and we’ve been doing our damnedest at trying to spend that money competently,” Goldstein says.

But mission scientists say they’re surprised so far by what the engineers have come up with. A lander might not be as tough as previously expected. Under one of the proposed designs, the lander would travel to Jupiter with the flyby spacecraft and then go into hibernation out near Callisto, away from heavy radiation. NASA would send in the lander after the flyby spacecraft had mapped the surface. Then, the lander would make use of two successful tech-nologies developed for Mars. A “Sky Crane” would lower the lander down toward the ice, where inflated balloons would bounce the spacecraft into a safe spot. The Sky Crane keeps the surface ice from

baking under rocket thrusters that would chemically alter the sur-face. The current design calls for a 10-day battery-powered mission, but scientists are considering adding solar panels to increase that life span. The instrument payload still has to go through a competitive application process; however, the “straw man” payload includes a gas chromatography mass spectrometer, which will be able to detect organics, as well as an infrared spectrometer.

“You’ve gone a long way and invested a lot of money and a lot of time and talent to get there,” Culberson says. “Why would you just send one instrument to check if there’s life in that ocean when they’ve got the ability to double check it with two instruments?”

Hand presented his study to NASA headquarters in January. At press time, the space agency was expected to announce a decision on the lander’s fate very soon.

There’s a lot more than Europa science at stake in the decision. Culberson says he sees the first lander as a “Daniel Boone precur-sor.” A decade after this mission, a follow-up spacecraft would actually attempt to venture into Europa’s oceans and look for black smokers. The congressman says he’s already tapped an expert in underwater exploration: Robert Ballard. A handful of researchers from JPL and elsewhere is examining how to melt through the ice. And the spacecraft developed for Europa will inform future mis-sions that will explore the other ocean worlds too. Culberson believes that developing that path is a crucial part of NASA’s mis-sion over the next decade.

“That’s all coming. That’s all a part of what I’m envisioning for the future,” Culberson says. “The groundwork I’m laying today brick by brick is intended to achieve these dreams, for the future and the far future, and it’s a wonderful thing to contemplate.”

Michael Benson used some 40 images taken by Voyager 1 on March 3, 1979, to create this mosaic of Europa with Jupiter’s Great Red Spot. NASA/

JPL/MICHAEL BENSON, KINETIKON PICTURES

Read Astronomy’s full Europa interview with U.S. Rep. John Culberson on page 16.

Sample return


Sample return

Friday, February 15, 2013, everybody was staring up at the sky. They were wait-ing for the record-breaking

close approach of asteroid 367943 Duende. This 100-foot-wide (30 meters) space rock was due to pass our planet at a distance of only 17,000 miles (28,000 kilometers), sweeping inside the ring of geostationary weather and communications satellites that keep pace above the equator. Then, while the world stared in one direction, a second asteroid shot in from behind and exploded above Chelyabinsk, Russia.

Pieces of the surprise asteroid fell to Earth to become meteorites. It was a siz-able 65 feet (20m) in diameter, and its fire-ball explosion lit up the morning sky brighter than the Sun. Buildings in six

neighboring cities were damaged and about 1,500 people sustained injuries needing hospital treatment. The shock left everyone asking one question: How could scientists know about Duende but have missed the approach of the Chelyabinsk asteroid?

Two missions, one goalThe answer goes far beyond one rogue asteroid, demanding that we understand intimately the composition and move-ment of distant, dark, orbiting rocks. Two space agencies are setting out to tackle the problem. This September, NASA will launch its Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft to the asteroids. It is a journey that runs hot on the heels of the Japanese Aerospace Exploration Agency’s (JAXA) asteroid mission, Hayabusa2. Both spacecraft are due to intercept their targets in 2018, with plans to touch down and gather rocks

When Rosetta landed on a

comet, the world held its breath. Now, scientists

are about to attempt an even more ambitious

mission — twice. by Elizabeth Tasker

Elizabeth Tasker is an astronomer at Hokkaido

University in Japan, building stars and planets in

her computer. She is on Twitter: @girlandkat.

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from the asteroid surfaces. These hand-fuls of pebbles will be incredibly precious because humans have retrieved pristine samples from only two surfaces beyond our planet: the Moon, using the full power of the Apollo program, and asteroid 25143 Itokawa, in a daring mission by Hayabusa2’s predecessor. And it is these pebbles that should shed light on the dif-ficult problem of tracking asteroids.

OSIRIS-REx and Hayabusa2 are head-ing for asteroids that orbit the Sun close to Earth. This classifies the two mission tar-gets as near-Earth objects (NEOs). Hayabusa2 is heading for an asteroid named 162173 Ryugu, a rock a little over half a mile (1km) across whose orbit does not pose any threat to our planet. The tar-get for OSIRIS-REx is the asteroid 101955 Bennu, about half Ryugu’s size but with a more risky future.

Most asteroids reside in the asteroid belt, a band of rocks that orbits the Sun between

Mars and Jupiter. Asteroids may leave this desirably distant location to approach Earth after collisions that scatter the rocks into different orbits. Their new routes through the solar system depend on gravitational tugs from the Sun and planets and the mys-teriously tricky effect of sunlight.

When sunlight strikes an asteroid, its surface absorbs the Sun’s energy and re-emits it as heat. There is a delay between these two events while the rock warms, dur-ing which time the asteroid rotates. This motion causes it to emit the heat in a differ-ent direction than when it absorbed the energy. The result is like catching a ball and throwing it to a person standing to your right. The small recoil from catching and throwing push in different directions, and you feel a force. For light particles called photons, this is called the Yarkovsky effect.

While the Yarkovsky effect also pushes on Earth, the force is too tiny to make any difference to our motion. Even on an

asteroid the effect is not large, but over time it can change the asteroid’s trajectory enough to make it a real problem.

The direction and strength of the Yarkovsky sunlight push depend on the type of rock and its shape. Different mate-rials have different heating and cooling rates, and surface topography may place part of an asteroid permanently in shadow. This is the crux of why asteroid motion is so hard to predict: Scientists do not know enough about asteroid composition to accurately calculate the Yarkovsky force.

Bennu is currently orbiting the Sun between Venus and Mars on a path that brings it close to Earth every six years.

Two spacecraft from two nations — Hayabusa2 from Japan (left) and OSIRIS-REx from the United States (below) — will make their way to small, dark, moving asteroid targets. But the most audacious part of the missions comes when they attempt to return bits of their asteroids home to Earth.

Sunlight

Orbitalpath

Rotation

The Sun-exposed surface of the asteroid heats up

New path

Direction fromheat release

Release of heat

Old path

Venus

Ryugu

Mars

Earth

Mercury

Venus

Bennu


While the asteroid is not in immediate danger of hitting our planet, there is a 1 in 2,500 chance that it will strike Earth in the late 22nd century. This is one of the highest probabilities of any known asteroid.

Scientists cannot be more precise about Bennu’s fate without knowing more about the force from the Yarkovsky effect. It is one thing to predict Bennu’s motion a few years out, but decades of cumulative Yarkovsky effects will make its position less certain 200 years in the future. A major goal for OSIRIS-REx is to record Bennu’s motion accurately enough to measure sunlight’s push. This will both constrain Bennu’s future path and make vital improvements to the predictions for other NEOs.

The beginnings of lifeYet the threat of an Armageddon impact from an unknown asteroid is only half of the reason for these twin missions. Examinations of meteorites have revealed that many once contained water, leav-ing them packed with organic molecules. These finds open the door to the intrigu-ing possibility that life on Earth may have come from space.

Exactly how life began on Earth remains unknown. In most formation the-ories for our solar system, Earth’s building blocks were dry grains too warm to con-tain the amounts of water the planet boasts today. The young desert Earth then gained its oceans from the arrival of ice-laden meteoroids. It is possible that this water delivery also contained the first organic molecules. To prove this theory, scientists need to find a similar icy rock while it is still in space, uncontaminated by the now-biologically active Earth.

There are two main reservoirs for mete-oroids that are siblings to the ones that hit early Earth. The first are the comets that originate from beyond Neptune. Consisting mainly of ice, comets grow their distinctive tail as they travel toward the heat of the

Sun. But measurements of the vapor sur-rounding comet nuclei suggest they were not our water delivery service.

Most cometary water contains too much deuterium, a heavy version (with a neutron) of the hydrogen atom (no neutron) that bonds with oxygen to make a water mol-ecule. In December 2014, based on its stud-ies of Comet 67P/Churyumov-Gerasimenko, the European Space Agency’s Rosetta team concluded it was unlikely our oceans came from the comet population.

The second option is asteroids. Ground-based observations of Ryugu suggested the asteroid might contain water-rich minerals that must have formed in wet conditions. While Ryugu is too small to support liquid water, water in its parent asteroid may have left it full of organic molecules.

The same may also be true of Bennu. Both asteroids are carbonaceous chon-drites, a class that formed in the early days of the solar system and has remained nearly unchanged during the past 4.5 bil-lion years. This makes them kin to the meteorites that struck early Earth. It is therefore a good bet that any molecule found on these bodies would have also been delivered to our planet in its past.

Touching the asteroidsOSIRIS-REx and Hayabusa2 will arrive at their respective targets in 2018. Then they will begin intensive 1.5-year analyses of their asteroids, exploring their structure from the largest scales down to surface grains smaller than a millimeter. Yet the most daring moments will be when the two spacecraft touch down on the asteroid surfaces.

When Rosetta visited Comet 67P, it dispatched the Philae lander to the surface to make a one-way trip, which went awry when the probe bounced repeatedly, landing on its side in a dark shadow. But in order to return asteroid samples to

Earth, OSIRIS-REx and Hayabusa2 must land the main spacecraft to gather material and then safely take off back into space. The small surface area of the asteroids, their weak gravity, and the unknown sur-face composition make this a dangerous endeavor, and failure could cost a mission its whole spacecraft. However, this mam-moth task has been undertaken success-fully once before.

As its name implies, Hayabusa2 has a predecessor. The first Hayabusa spacecraft returned to Earth in June 2010, bringing with it samples from asteroid Itokawa.

Like the Rosetta mission, Hayabusa did not have an easy time landing in the low-gravity environment of such a small rock. The spacecraft was designed to make only a brief touchdown on the asteroid’s surface, but a malfunction caused it to bounce just as Philae did a decade later. When Hayabusa

Japanese Aerospace Exploration Agency scien-tists successfully test Hayabusa2’s Small Carry-on Impactor. They plan to use it to blow a 33-foot (10 meters) crater in asteroid Ryugu to collect samples from its interior. JAXA/NIHONKOHI

Crossing pathsRyugu and Bennu have Earth-crossing orbits, but Bennu’s has a much higher chance of impacting Earth in a few centuries. ASTRONOMY: ROEN KELLY

The Yarkovsky effect describes how light can change an object’s path by pushing it in one direction when the object absorbs light, and in another when the object later emits the energy as heat.

Asteroid motion is tough to predict

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fell back to the asteroid’s surface, it stayed there for half an hour, exposing itself to tem-peratures far beyond its design specification.

Despite this, Hayabusa survived to make a second successful landing attempt. It returned to Earth to bring back the first grains from an asteroid. Unlike Ryugu and Bennu, Itokawa has changed greatly since its formation and contains no signs of water or organic molecules. What it did provide was a resource on how sunlight can weather an asteroid’s surface — information that will be key to understanding the observa-tions from OSIRIS-REx and Hayabusa2. Its return also highlighted the importance of such sample retrieval missions.

“The images of these tiny grains appeared and were instantly recognizable to petrologists,” says Harold Connolly, the mission sample scientist for OSIRIS-REx, as he describes the presentation of the results from Hayabusa. “It was a fixed moment in time for me.”

It was a discovery that never would have been as obvious from an analysis performed remotely in space. Connolly realized that to understand our planet’s past and future, he had to return to the asteroids.

The mechanism for collecting these vital grains is different between the two current missions. OSIRIS-REx will touch down at the end of its mission in 2019. When it lowers onto Bennu’s surface, an extended mechanical arm will release a strong jet of nitrogen gas. As the jet hits the surface, loose rocks and grains will be stirred up and collected in the sample

chamber at the end of the arm. “Our col-lector is a lot like a vacuum cleaner or Hoover,” explains Connolly. “It will sweep up rock particles on the surface of Bennu using an inert gas.” This inert gas will not contaminate or change the samples scien-tists need for their studies.

To check that this system will work in the vicinity of the asteroid, NASA scien-tists tested the equipment back on Earth in the so-called “vomit comet.” Named for its effect on the stomach of human passen-gers, the airplane mimics the low-gravity environment of space through regular dips in its flight.

The cleaning job will yield a sizable haul of rocks for OSIRIS-REx — between 2 ounces and 4 pounds (60 grams to 2 kilo-grams) of differently sized particles. The plan is to perform this challenging landing only once, but OSIRIS-REx is equipped to try three times if there are any problems.

Hayabusa2 has a different game plan. The spacecraft intends to land not just once, but three times on Ryugu. By gathering material at different sites, Hayabusa2 will sample any variation in the asteroid’s composition. It is a schedule that increases the risk to the spacecraft, but then, Japan has done this before.

Scientists work on the nearly complete Hayabusa2 spacecraft prior to its launch. JAXA

Hayabusa2 launched December 3, 2014, and is already well on its way toward asteroid Ryugu and set to arrive in 2018. JAXA

OSIRIS-REx displays its high-gain antenna and solar arrays before engineers move it from construction to environmental testing in October 2015. LOCKHEED MARTIN CORP.


To stir up the surface material for col-lection, Hayabusa2 will fire a bullet into the asteroid as it touches down for its first two landings. At least one of these loca-tions will be at the site of the observed water-rich minerals, while the second will be selected after Hayabusa2 has scouted the asteroid from above.

On the third landing, the spacecraft plans to gather material from deeper inside Ryugu’s belly. For that, a larger explosion is needed. Hayabusa2 is carrying a “Small Carry-on Impactor” containing 10 pounds (4.5kg) of explosives. When it hits the asteroid, the resulting blast will carve a crater up to 33 feet (10m) across. To protect itself from the explosion, Hayabusa2 will duck behind the asteroid, dispatching a camera to monitor the result in its stead.

Then the spacecraft will make its final col-lection from the freshly exposed rock.

While Hayabusa2 cannot linger on the surface, it will leave behind a lander packed with three rovers. These robotic explorers will examine Ryugu’s surface in greater detail and test the challenges of motion in a low-gravity environment.

Hayabusa2 is aiming for a smaller sample yield than OSIRIS-REx, with a minimum weight of 100 milligrams. Small though this sounds, the first Hayabusa mission revealed an enormous amount of information about the asteroid, Itokawa, with roughly 10,000 times less material. A tenth of a gram is sufficient for all the analysis the mission needs to complete, although the team’s best-case scenario will see several grams returned to Earth.

Samples from the three sites will be stored separately inside Hayabusa2’s container, which will be completely sealed to prevent contamination from terrestrial molecules upon return to Earth. Hayabusa2 is due to land in the Australian outback at the end of 2020, while OSIRIS-REx will land in the Utah desert in 2023. When the containers are cracked open, the science teams will be looking into time capsules from the earliest days of our solar system.

TeamworkHaving independent data from two aster-oids greatly reduces the possibility that the collected sample is not typical of the objects. This allows for scientists to draw much bigger deductions from the data. “Samples from two asteroids more than doubles their worth,” states Connolly.

Because of this, NASA and JAXA officially joined the OSIRIS-REx and Hayabusa2 missions with a “Memorandum of Understanding.” The two teams will share expertise and exchange a fraction of the samples from each mission. JAXA will send 10 percent of the Hayabusa2 samples from Ryugu to NASA, which in turn will send half a percent of the OSIRIS-REx Bennu sample to JAXA. The difference in the figures reflects OSIRIS-REx’s larger sample size, and the fact that JAXA will make use of NASA’s Deep Space Network of commu-nication antennas to track Hayabusa2 on its journey.

Hayabusa2’s first landing on Ryugu will come a year before OSIRIS-REx touches down on Bennu. Both teams will be glued to the data so that they can prepare for any surprises in their future landings. In return, the OSIRIS-REx team is sharing its software to construct three-dimensional

NASA scientists overlaid simulated craters and topography on real radar images of asteroid Bennu, with an artist’s depiction of OSIRIS-REx in flight next to it. Genuine high-resolution images will not arrive until shortly before the spacecraft itself does in 2018. NASA/JPL/GOLDSTONE/GSFC/UA/MIKE NOLAN (ARECIBO

OBSERVATORY)/BOB GASKELL (PLANETARY SCIENCE INSTITUTE)

Hayabusa2 will shoot an explosive charge into asteroid Ryugu and then flee to the space rock’s far side to avoid damage when it blows. The space-craft will return to sweep up the pulverized material churned up from deep inside the asteroid’s bulk. AKIHIRO IKESHITA

WHAT’S IN A NAME?

BennuIn 2013, the Planetary Society

held a naming contest for the

asteroid 1999 RQ36

. The winner

was 9-year-old Mike Puzio, who

submitted the name Bennu, an

Egyptian deity depicted as a

heron in mythology and associ-

ated with the god Osiris. In addi-

tion to the mythological pairing,

Puzio also thought the space-

craft resembled a bird in flight,

and the asteroid itself an egg.

RyuguThe Japanese space agency

renamed its target from 1999 JU3

to Ryugu in 2015, also based on

public submissions. In Japanese

folklore, the hero Taro Urashima

retrieves a treasure chest from a

dragon-guarded castle named

Ryugu at the bottom of the sea.

Likewise, astronomers count on

Hayabusa2 to bring back treasures

that will inform them about Earth’s

oceans. — Korey Haynes


models of asteroids to assist Hayabusa2 in its navigation.

Both agencies strongly support this col-laboration, as revealed in a meeting between the director general of the Institute of Space and Astronautical Sciences at JAXA, Saku Tsuneta, and OSIRIS-REx’s principal inves-tigator, Dante Lauretta, in October 2014. “For a center director to reach out and dis-cuss a particular science expedition is unprecedented,” says Connolly, who was also at the meeting.

Connolly has been working extensively with his sample collection counterpart on the Hayabusa2 mission, Shogo Tachibana. The two agree that the collaboration is rewarding but not always easy.

The differences in size between the two space agencies has raised questions about the balance of power. Japan initially voiced concerns that a collaboration with NASA would result in the larger agency dominat-ing both asteroid missions. But Japan’s expertise in asteroid missions and meteor-ite science balances the scale. “In asteroid research, we can make this an even col-laboration between us,” Tachibana states.

But JAXA’s smaller size contributes other more subtle factors to the work cul-ture as well. “Japan is used to working alone,” explains Tachibana. “We operate more as a family than a corporate business, where everyone’s role is implicitly under-stood. But a company the size of NASA requires detailed contracts for all aspects of the research.”

Such cultural differences don’t exist only within the mission teams. Connolly describes his experience during a visit to Japan when a bartender found out that Tachibana was a member of the Hayabusa2 mission. “This guy went down on one knee to shake Shogo’s hand,” he says. “That

would never happen in America! There is a huge difference in perception.”

Yet despite these mismatches in size and recognition, NASA and JAXA are taking similar steps to reach beyond the scientific community. Both organizations held public naming competitions for their asteroid tar-gets. Additionally, the OSIRIS-REx team is organizing a citizen science project to help identify NEOs. Project “Target Asteroids!” asks amateur astronomers to send in images of asteroids to increase researchers’ knowl-edge of these poorly understood objects. The two missions keep their websites busy with animated videos, interviews with project scientists, and mission updates. Much of JAXA’s outreach takes place in Japanese, of course, but they also run an English Twitter feed and share news on the mission website in both languages.

Even with all the differences interna-tional collaborations can bring, there is no doubt in the minds of the OSIRIS-REx and Hayabusa2 teams of the worth of this part-nership. The samples OSIRIS-REx and Hayabusa2 will bring home contain the history not of a single country, but of all life on Earth, and keys to its future as well. Both groups want to ensure the best exper-tise is waiting to receive it.

An artist envisions OSIRIS-REx releasing its Sample Return Capsule when it returns to Earth. It should land in the Utah desert in 2023.

OSIRIS-REx will reach out its sample collector like a vacuum cleaner extension (inset) to gather sam-ples from asteroid Bennu’s surface, possibly retrieving up to a few pounds. NASA GODDARD SPACE FLIGHT CENTER

Exactly a year after its launch on December 3, 2014, Hayabusa2 performed an Earth flyby on its way to asteroid Ryugu, capturing this image at a distance of 340,000 kilometers (211,000 miles).

Hayabusa2 will return its samples in 2020, when they plummet to the Australian outback.

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A: In the early 1990s, two

teams of astronomers set out to

measure the universe’s expan-

sion history to predict its

future. If the universal expan-

sion was slowing down a lot, it

would someday stop and

reverse itself, ending in a hot

Big Crunch. If, instead, the

deceleration was small, the

universe would expand forever

(albeit at a decelerating rate).

Each of these possibilities

predicted a different relation-

ship between the distances (or,

more precisely, “lookback

times”) of galaxies and their

redshifts (the amount the uni-

verse had stretched while the

light was on its way to us).

Redshifts are easy to mea-

sure from spectra of galaxies,

except when the galaxies are

faint. Astronomers obtain dis-

tances of nearby galaxies by

finding a star of known lumi-

nosity (power), measuring its

apparent brightness, and

applying the inverse-square law

of light. But at great distances,

normal stars can’t be seen, so

the astronomers used Type Ia

supernovae — exploding stars

resulting from white dwarfs

that approach their maximum

possible mass (the Chan-

drasekhar limit). These can be

billions of times as powerful as

the Sun, and their peak lumi-

nosities are nearly uniform.

The two teams used large

telescopes to take deep images

of various parts of the sky,

repeating these same fields a

few weeks later. They found

supernova candidates among

the thousands of faint galaxies.

They then obtained spectra of

the candidates to confirm that

they were Type Ia supernovae

and to obtain their redshifts.

By repeatedly imaging these

supernovae, they measured

their light curves and peak

Astronomy’s experts from around the globe answer your cosmic questions.

EXPANSION EXPLAINED

brightnesses. The teams also

took issues into account such

as the nonuniformity of Type

Ia supernovae, the presence

of intervening dust, and pos-

sible cosmic evolution of

supernovae.

The result was that the

supernovae were too faint (for a

given redshift) to be consistent

with decelerating or constant-

speed expansion of the uni-

verse. Instead, the data implied

that the expansion has been

accelerating in the past 5 billion

years. (Later measurements

revealed the era of deceleration

during the first 9 billion years.)

Other techniques have now

confirmed this acceleration,

which most astrophysicists

attribute to the presence of dark

energy of unknown origin.

Alex Filippenko

Professor of Astronomy

University of California, Berkeley

Q: COULD THE CHICXULUB

ASTEROID HAVE HELPED TO

TRIGGER THE VOLCANIC

ACTIVITY IN THE DECCAN

TRAPS 65 MILLION YEARS

AGO?

Bruce Maier

Shoreham, New York

A: Scientists are still searching

for the answer to this long-

standing planetary science

question. At the moment, it

depends on whom you ask.

What we do know is that 66

million years ago, an asteroid

smashed into modern-day

Mexico near the tiny town of

Chicxulub. Land turned to

liquid. Twelfth-magnitude

earthquakes launched land-

slides across the Western

Hemisphere. And a climate-

altering dust blanket enveloped

Earth, killing much of its life,

including the dinosaurs.

At the same time this catas-

trophe was playing out, floods

of lava were seeping from the

ground in modern-day West

India. Scientists estimate that

each eruption lasted years —

even decades — over the course

of hundreds of thousands of

years, producing one of Earth’s

largest volcanic features.

A recent University of Cali-

fornia, Berkeley study published

in Science suggested that the

impact altered Earth’s magma

plumbing, accelerating the vol-

canoes in India for 500,000

years and giving dinosaurs a

one-two punch. Exactly how

that’s possible is still unclear.

ASKASTR0

Q: HOW DID ASTRONOMERS DISCOVER

THAT THE EXPANSION OF THE UNIVERSE

WAS ACCELERATING? Steve Ciucci, Madison, Wisconsin

Some geologists say dinosaurs were killed by the one-two punch from an asteroid impact followed by some of the most incredible volcanic eruptions known. Scientists recently showed the Deccan Traps, shown here outside Mumbai, India, erupted within 50,000 years of the asteroid impact.

Astronomers used distant supernovae to determine that the expansion of our universe was speeding up. NASA/ESA, THE HUBBLE KEY PROJECT TEAM AND THE HIGH-Z

SUPERNOVA SEARCH TEAM

MA

RK

RIC

HA

RD

S/U

C B

ER

KE

LE

Y


And not everyone’s buying

that answer. Another study

published in Nature Geoscience

earlier in 2015 showed that sul-

fur dioxide emissions from the

Deccan Traps would have had

a limited influence on Earth’s

atmosphere, because it would

require long-lasting and unin-

terrupted eruptions to alter

climate or cause widespread

acid rain.

A new scientific drilling

expedition to the Chicxulub

crater this spring could help

finally clear up the confusion.

Eric Betz

Associate Editor

Q: IS OUR SOLAR SYSTEM

WITHIN THE MILKY WAY

BAND THAT WE SEE OVER-

HEAD ON A CLEAR NIGHT?

Edmund Walendowski

Charlottesville, Virginia

A: Yes. Our solar system lies

just above the Milky Way disk

midplane. The bright band

that we can see on a clear night

is the disk of our home galaxy,

and we are inside it. The

brightness comes from the fact

that most stars are in this disk.

However, it also contains gas

and dust from which stars

form. Unfortunately, this

material blocks our view in

some wavelengths, especially

in the visible band. In this

sense, the development of

infrared detectors in recent

decades has boosted our

knowledge of the galactic

structure.

To get an idea of what hap-

pens when you look at the

Milky Way, picture yourself in

a fog. If the fog is not dense,

you probably will be able to see

nearby objects, but the fog will

completely obscure the more

distant ones. The dust in the

galactic disk is much less dense

than a fog, thus you cannot see

dust in your neighborhood.

For large distances, however,

the dust accumulation along

the line of sight becomes sig-

nificant, blocking your view

completely. The dust density

increases toward the galactic

center — the fog becomes

thicker.

One final point. The Sun’s

location within the dust-

obscured disk complicates

observations of the structure

of our galaxy since we don’t

have a bird’s-eye view of the

Milky Way.

Denilso Camargo

Federal University of

Rio Grande do Sul

Porto Alegre, Brazil

Q: WHEN ASTRONOMERS

TALK ABOUT ALL THE DUST

AND GAS IN THE UNIVERSE,

WHAT KIND OF “DUST” ARE

THEY ACTUALLY TALKING

ABOUT?

Bob Safir

Sherman Oaks, California

A: Dust may generally be

described as particles small

enough to be lifted into the air.

In our homes, we are the big-

gest source of dust. Next to

plant pollen, household dust

consists mostly of hair and

skin cells as well as dust mites

that eat these and add their

feces to the dust. Outside our

homes, atmospheric dust can

be mineral dust, such as from a

desert dust storm or a volcanic

ash cloud, or from natural or

industrial burning processes.

Gas clouds that astronomers

talk about consist of hydrogen

and helium, the most abun-

dant elements in the universe.

These gas clouds can collapse

under their own gravity and

form a star. The inside of that

star is so dense that hydrogen

is fused into helium (in Sun-

like stars) and into heavier

elements such as carbon, oxy-

gen, and eventually iron (in

more massive stars).

When a massive star

explodes at the end of its life as

a supernova, even heavier ele-

ments form, and these spread

out to eventually mingle with

another gas cloud.

Hydrogen and oxygen can

now combine into H2O; carbon

and oxygen form CO2. Carbon,

hydrogen, and other light ele-

ments form organic molecules,

often referred to by astrono-

mers as the building blocks

of life. The ingredients form

molecular clouds. Heavier

elements like iron and silicon

combine with oxygen to form

minerals, and we refer to these

tiny mineral grains as dust.

Water ice or organic molecules

can then stick to these dust

particles.

Our solar system formed

from a gas and dust cloud.

While gas giants like Jupiter

and Saturn are mostly hydro-

gen and helium, it took a lot of

dust and whatever stuck to it

to form rocky planets like

Earth and Mars.

Christian Schroeder

University of Stirling

Scotland

Send us your questions Send your astronomy

questions via email to

[email protected],

or write to Ask Astro,

P. O. Box 1612, Waukesha,

WI 53187. Be sure to tell us

your full name and where

you live. Unfortunately, we

cannot answer all questions

submitted.

This 340 million-pixel view of the Milky Way’s center was taken from Cerro Paranal in Chile as part of the European Southern Observatory’s GigaGalaxy Zoom project. ESO/S. GUISARD

TRIANGULUM

TAURUS

PERSEUS

ARIES

April 18, 45 minutes after sunsetLooking west-northwest

Aldebaran

Mercury

5°

Mercury stars at dusk


Visible to the naked eye

Visible with binoculars

Visible with a telescope

MARTIN RATCLIFFE and ALISTER LING describe the solar system’s changing landscape as it appears in Earth’s sky.

April 2016: Mercury reaches its peak

SKYTHISMONTH

While folklore implies that sky-watchers might have to dodge April showers, the

effort will be worth it. Several planets put on great shows this month, shining brightly and providing visual feasts for those with telescopes. Jupiter leads the way, dominating the sky from dusk until close to dawn, while Mars and Saturn take center stage after midnight.

But we’ll begin our solar system tour with a more chal-lenging object. Mercury has its best evening appearance of the year during April. That’s because in early spring the ecliptic — the path of the Sun across our sky that the planets follow closely — tips steeply to the western horizon after sun-set, so a planet’s separation

night. Mercury remains a tempting target from roughly 10 days before greatest elonga-tion until a week after. Pay particular attention on the 8th when a waxing crescent Moon passes by. The planet shines at magnitude –1.0 and lies 8° to our satellite’s lower right.

As twilight fades, observers will shift their attention to Jupiter. The giant planet reached opposition and peak visibility in March, but its appearance in April hardly suffers. The biggest difference is its improved visibility: By the time darkness falls, Jupiter already has climbed 40° high in the southeast.

The giant world spends the month in southern Leo, some 15° east-southeast of 1st-magnitude Regulus. At magnitude –2.4, Jupiter out-shines the Lion’s luminary by more than 30 times.

A telescope reveals stun-ning detail in the planet’s cloud tops. Jupiter’s equator spans 42" at midmonth, an almost imperceptible 2"

from our star translates largely into altitude.

As the innermost planet, however, Mercury still never escapes the twilight glow. At greatest elongation April 18, it lies 20° east of the Sun and stands 10° high in the west-northwest 45 minutes after sunset. The world glows at magnitude 0.1 and shows up easily against the darkening sky. A telescope reveals Mercury’s 8"-diameter disk, which appears slightly more than one-third illuminated.

Of course, you don’t have to limit your viewing to one

smaller than at opposition. Notice that the planet doesn’t appear perfectly round. The diameter through the poles is nearly 3" less than across the equator.

The planet’s atmosphere sports two dark bands that straddle a brighter equatorial zone. The zone rotates about five minutes faster than the rest of the planet, so it’s little wonder that turbulence reigns at the belts’ edges. Many fea-tures change in one rotation.

As you gaze at Jupiter through a telescope, you can’t help but see its entourage of four bright moons. Typically these satellites appear against the black of space near the planet. Once each orbit, how-ever, a moon passes in front of Jupiter (a transit), and observers can watch its disk and inky-black shadow (a shadow transit) cross the planet’s face. A half-orbit later, the moon disappears behind the gas giant’s disk (an occul-tation) and then enters the planet’s shadow (an eclipse).

Earthbound observers get superb views of Mercury in mid-April, though the detail will pale in comparison to what the MESSENGER spacecraft captured up close. NASA/JHUAPL/CIW

The innermost planet shines brightly in twilight at midmonth as it puts on its best evening show of 2016. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY

Martin Ratcliffe provides plane-

tarium development for Sky-Skan,

Inc., from his home in Wichita,

Kansas. Meteorologist Alister

Ling works for Environment

Canada in Edmonton, Alberta.

Deneb

Vega

Altair

LYRA

CYGNUSAQUILA

Radiant

10°

April 23, 1 A.M.Looking east

Lyrid meteor shower

Mercurius, Messala, and Lacus Spei


As the evening sky darkens April

9, the crescent Moon stands

about 15° high in the west. Pull

your attention away from the

chain of craters arrayed along

the terminator — the line that

divides lunar day from night —

and hunt instead for Lacus Spei

(Lake of Hope).

Start at the prominent Mare

Crisium (Sea of Crises) near the

northeastern limb. Head a full

mare diameter north, and you’ll

land on the timeworn crater

Messala. Billions of years of bom-

bardment have rounded and

softened its once-sharp rim. Just

a short distance to the north is

the smaller crater Mercurius,

which sports a taller and sharper

rim indicating a more recent

impact. When the atmosphere

steadies, you’ll notice slumped

terraces at the base of its walls.

Although smaller craters typi-

cally hold their form, larger ones

collapse inward under the force

of gravity.

Lunar cartographers dubbed

the flat gray splotch that lies

between these craters the Lake

of Hope, which marked a

refreshing change from the

darker names they applied to

many of the maria. Two small

craters on the lake’s eastern

shore appear quite sharp, signi-

fying that they are the relatively

new kids on the block.

Keep watching Lacus Spei to

see how it darkens with each

passing night. As the Sun rises

higher in the lunar sky, shadows

disappear, and the surrounding

terrain brightens quickly. This

gives the impression that the

lava floor has darkened, but it’s

only a contrast effect.

Look for another transition as

the Lake of Hope approaches the

limb. Starting April 14 and run-

ning through Full Moon on the

22nd, our sister world appears

to be rotating to the northeast.

Astronomers call this motion

libration, and it results from the

Moon’s changing position rela-

tive to Earth’s orbit. During this

week, Luna climbs north of our

joint orbit around the Sun, so

from our perspective, its north-

ern hemisphere tilts away.

RISINGMOON

METEORWATCH

The April 22 Full Moon nearly ruins

this year’s peak of the annual Lyrid

meteor shower. The best views

likely will come just before twilight

begins. The meteors appear to

radiate from the constellation Lyra,

which then lies nearly overhead,

and the Moon then hangs low in

the southwest. If you face away

from our satellite, you should see

a few “shooting stars.”

You might have just as much

luck the morning of April 12. That’s

when the minor Virginid shower

peaks. With the Moon setting just

after midnight, observers at dark

sites could see up to five meteors

per hour coming from near Spica.

Hope springs eternal near the lunar limb

The Lyre plays a melancholy tune

— Continued on page 42

Lyrid meteorsActive dates: April 16–25

Peak: April 22

Moon at peak: Full

Maximum rate at peak: 18 meteors/hour

On the action-packed night of April 6/7, Jupiter viewers can witness all four kinds of events. Innermost Io begins to transit Jupiter at 9:52 p.m. EDT, and its shadow follows 40 minutes later. Keep your eyes on Europa west of the planet — Jupiter occults this moon at 10:48 p.m. Gany-mede, the solar system’s larg-est satellite, then lies east of Jupiter but is closing rapidly. It starts to transit the gas giant at 1:01 a.m.

There’s more on tap if you stay up to the wee hours. At 2:54 a.m., Europa emerges from Jupiter’s shadow about one planet radius east of the limb. Ganymede then appears more than halfway across the jovian disk. Its large shadow first touches the cloud tops at 3:45 a.m. Ganymede’s transit ends a half-hour later, by which time Jupiter is sinking

Lyrid meteors have to fight hard to show up under the glare of this month’s Full Moon, but observers should still see a few “shooting stars.”

The dark lava of Lacus Spei stands out as the Sun climbs higher in the lunar sky in April’s second week. CONSOLIDATED LUNAR ATLAS/UA/LPL; INSET: NASA/GSFC/ASU

The middle of April provides observers at mid-northern latitudes with their finest evening views of Mercury this year.

OBSERVING HIGHLIGHT

N

E

Mercurius

Lacus Spei

Messala

LE

O

MI

NO

R

A N T LH Y D R A

C R AT E R

VI R

GO

CA

NE

S

VE

NA

TIC

I

BO

ÖT

ES

CO

MA

BE

RE

NI

CE

S

S E X TA N S

V E

LEO

C O RV U S

CO

RO

NA

B

OR

EA

LI

S

C E N TAU R U S

SE

RP

EN

S

CA

PU

T

OP

HI

UC

HU

S

LIB

RA

UR

SA

MA

JOR

CASSIOPEIA

PARDALIS

URSA

MINOR

CEPHEUS

HE

RC

UL

ES

CYG

NU

S

LY

RA

DRACO

Spica

Arctu

rus

M104

M83

M5

M64

NG

P

Denebola M65 M66

Reg

ulu

s

M51

M1

3

Mizar

NCP

M82

M81

Vega

Polaris

C

NGC 5128

Jupiter


STARDOME

Sirius

0.0

1.0

2.0

E

S

NE

SE

3.04.05.0

STAR

MAGNITUDES

N

STAR COLORS

A star’s color depends

on its surface temperature.

• The hottest stars shine blue

• Slightly cooler stars appear white

• Intermediate stars (like the Sun) glow yellow

• Lower-temperature stars appear orange

• The coolest stars glow red

• Fainter stars can’t excite our eyes’ color

receptors, so they appear white unless you

use optical aid to gather more light

How to use this map: This map portrays the

sky as seen near 35° north latitude. Located

inside the border are the cardinal directions

and their intermediate points. To find

stars, hold the map overhead and

orient it so one of the labels matches

the direction you’re facing. The

stars above the map’s horizon

now match what’s in the sky.

The all-sky map shows

how the sky looks at:

midnight April 1

11 P.M. April 15

10 P.M. April 30

Planets are shown

at midmonth

1 2

3 4 5 6 7 8 9

10 11 12 13 14 15 16

17 18 19 20 21 22 23

24 25 26 27 28 29 30

SUN. MON. TUES. WED. THURS. FRI. SAT.

CA

NI

S

MI

NO

R

PY

XI S

CA

NC

ER

PU

PP

IS

MO

NO

CE

RO

S

L IA

E L A

TA

UR

US

GE

MI

NI

OR

IO

N

CA

MELO

PA

PE

RS

EU

S

LY

NX

AU

RIG

A

M4

4

M3

5

Po

llu

x

Cas

tor

NGC 884

Capella

M38

M

36

M3

7

Pro

cyo

n

M1

Be

telg

eu

se

M47

NGC 869

Path o

f the S

un (ecl

ipti

c)


Open cluster

Globular cluster

Diffuse nebula

Planetary nebula

Galaxy

W

NW

SW

MAP SYMBOLS

Note: Moon phases in the calendar vary in size due to the distance from Earth and are shown at 0h Universal Time.APRIL 2016

Calendar of events

4 The Moon passes 1.9° north of

Neptune, 9 P.M. EDT


Venus, 4 A.M. EDT

7 New Moon occurs at

7:24 A.M. EDT

The Moon is at perigee (221,931

miles from Earth), 1:36 P.M. EDT

8 The Moon passes 5° south of

Mercury, 7 A.M. EDT

The Moon passes 0.02° north of

asteroid Vesta, midnight EDT

9 Uranus is in conjunction with

the Sun, 5 P.M. EDT


Aldebaran, 6 P.M. EDT

13 First Quarter Moon

occurs at 11:59 P.M. EDT

16 Mars is stationary, 10 P.M. EDT

18 The Moon passes 2° south of

Jupiter, 1 A.M. EDT

Pluto is stationary, 9 A.M. EDT

Mercury is at greatest eastern

elongation (20°), 10 A.M. EDT

21 The Moon is at apogee

(252,495 miles from Earth),

12:05 P.M. EDT

22 Full Moon occurs at

1:24 A.M. EDT

Lyrid meteor shower peaks

24 The Moon passes 5° north of

Mars, midnight EDT

25 The Moon passes 3° north of

Saturn, 3 P.M. EDT

26 Asteroid Juno is at opposition,

11 P.M. EDT

28 Mercury is stationary,

midnight EDT

29 Last Quarter Moon

occurs at 11:29 P.M. EDT

SPECIAL OBSERVING DATE

25 The waning gibbous Moon lies within 10° of Mars, Saturn, and Antares in the predawn sky.

ILLU

ST

RA

TIO

NS

BY

ASTRONOMY

: RO

EN

KE

LLY

BEGINNERS: WATCH A VIDEO ABOUT HOW TO READ A STAR CHART AT www.Astronomy.com/starchart.

PATHOF THE

PLANETS

The planets in the sky

These illustrations show the size, phase, and orientation of each planet and the two brightest dwarf planets

for the dates in the data table at bottom. South is at the top to match the view through a telescope.

The planets in April 2016

ARI

CET

FOR

SCL

GRU

PsA

AND

TRI

CAS

PEG

SGE

L AC

AQR

CAP

MICC rA

SGR

SCT

SERAQL

LYR

CYG

VUL

CRT

UM a

SC O

OPH

HER

DR A

CEN

CRV

C OM

CV N

BO Ö

C rB

SER

VIRLIB

LUP

PSC

Objects visible before dawn

Celestial equator

Dawn MidnightMoon phases

Sun

Uranus

Pluto Saturn

Neptune

Ceres

J

Venus

Mars

The Moon slides past Mars, Saturn, and Antares before dawn April 25 Hygiea

Path of the Moon

123456789

192021222324252627282930

Venus

MarsMercury

Ceres

Uranus

SaturnNeptune

Pluto

10"

S

W E

N

Jupiter


Planets MERCURY VENUS MARS CERES JUPITER SATURN URANUS NEPTUNE PLUTO

Date April 15 April 15 April 15 April 15 April 15 April 15 April 15 April 15 April 15

Magnitude –0.4 –3.8 –1.0 9.2 –2.4 0.3 5.9 7.9 14.2

Angular size 7.0" 10.1" 13.8" 0.4" 42.5" 17.8" 3.4" 2.2" 0.1"

Illumination 51% 97% 95% 99% 100% 100% 100% 100% 100%

Distance (AU) from Earth 0.955 1.658 0.681 3.829 4.640 9.357 20.965 30.666 32.925

Distance (AU) from Sun 0.332 0.727 1.569 2.965 5.434 10.023 19.966 29.957 33.079

Right ascension (2000.0) 2h44.9m 0h43.7m 16h28.0m 0h12.8m 11h03.0m 16h59.3m 1h16.7m 22h50.7m 19h14.0m

Declination (2000.0) 18°29' 3°05' –21°14' –7°32' 7°39' –20°54' 7°28' –8°14' –20°52'

This map unfolds the entire night sky from sunset (at right) until sunrise (at left).

Arrows and colored dots show motions and locations of solar system objects during the month.

The planets in their orbitsArrows show the inner planets’

monthly motions and dots depict

the outer planets’ positions at mid-

month from high above their orbits.

Jupiter’s moonsIo

Europa

S

W E

N

Ganymede

Callisto

ILL

US

TR

AT

ION

S B

Y ASTRONOMY

: R

OE

N K

EL

LY

PSC

CET

SCL

FOR

CAE

ERI

CAS

AND

TRI

ARI

PER

AUR

TAU

ORI

COL

LEP

LYN

GEM

CNC

CMi

CMA

MON

PUPPYX

ANT

HYA

SEX

LEO

LMi

Objects visible in the evening

Early evening

Sun Jupiter

Mercury appears bright in the evening sky during mid-April

Comet Ikeya-Murakami (C/2010 V1)

Mercury

Path of the Sun (ecliptic)

789101112131415161718

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

Europa

Callisto

Io

Ganymede

Jupiter

MercuryGreatest eastern elongation

is April 18

Ceres

UranusSolar conjunction is April 9

Mars

Earth

Saturn

Pluto

Neptune

Venus

Jupiter

Jupiter


Dots display positions

of Galilean satellites at

11 P.M. EDT on the date

shown. South is at the

top to match

the view

through a

telescope.

To locate the Moon in the sky, draw a line from the phase shown for the day straight up to the curved blue line.

Note: Moons vary in size due to the distance from Earth and are shown at 0h Universal Time.

The planets in their orbitsArrows show the inner planets’

monthly motions and dots depict

the outer planets’ positions at mid-

month from high above their orbits.

Path ofComet Ikeya-

Murakami

April 1

6

11

16

21

26

May 1

LEO

31

Regulus

N

E

1°

Comet Ikeya-Murakami (P/2010 V1)

April 6, 10:45 P.M. EDT

JupiterGanymede

Io’s shadow

IoEuropa

S

W

15"

Shadow play at mighty Jupiter


COMETSEARCH

What do comets and galaxies

have in common? When viewed

through a 4-inch telescope under

a dark sky, the solar system

wanderers and distant island

universes often appear similar

in brightness and shape. The

resemblance inspired avid comet

hunter Charles Messier to catalog

non-stellar objects to help reduce

false alarms of comet discoveries.

Comet Ikeya-Murakami

(P/2010 V1) should glow around

10th magnitude this month, a

near match for many of the gal-

axies in Messier’s catalog. What’s

more, it lies among the back-

ground stars of Leo, within 40° of

more than 20 Messier galaxies.

The shape of Ikeya-Murakami

won’t remind too many observers

of a galaxy, however. Instead of

being round or slightly oval, it

should look dagger-shaped with

a bulbous end. Imagers might

capture a short greenish or bluish

gas tail sticking out the south-

eastern end. Meanwhile, the fan-

shaped dust tail turns almost

edge-on to our line of sight and

appears as a colorless streak to

the west of the nucleus. The

southern edge of the comet’s

head, or coma, will be sharper

than the northern flank. To see

the most detail, use as much

magnification as your scope and

the night’s conditions allow.

Ikeya-Murakami’s trajectory in

April carries it to the southeast

across western Leo and its con-

spicuous Sickle asterism. It slides

a mere 0.5° from 1st-magnitude

Regulus, the Lion’s heart, on April

24 and 25. Although the close

pass makes the comet easy to

locate, it will be hard to see in the

glare of the blue-white luminary.

Piercing the heart of the Lion

EVENING SKY MIDNIGHT MORNING SKY

Mercury (west) Mars (southeast) Venus (east)

Jupiter (southeast) Jupiter (southwest) Mars (southwest)

Saturn (southeast) Saturn (south)

Neptune (east)

WHEN TO VIEW THE PLANETS

— Continued from page 37

low in the west for observers in eastern North America.

Although the evening hours belong to Jupiter, the parade of planets starts to pick up around midnight local daylight time. Mars leads the way. It rises in the southeast just before mid-night April 1 and about two hours earlier by month’s end. Backyard observers have waited two years for Mars to return to glory. The Red Planet reaches opposition in late May, so both its brightness and apparent size through a telescope ramp up quickly this month.

As April opens, Mars shines at magnitude –0.5 among the background stars of northern

apparent size. If you target the Red Planet through a scope on April 1, you’ll see a disk 12" across. Repeat the observation on the 30th, and Mars will span 16".

Don’t be fooled, however. This is still small, and surface details appear subtle. Your local observing conditions play a big role in how clearly fea-tures show up. For a good look, wait until Mars climbs at least 20° high roughly two hours

Scorpius. It then heads east-ward, crossing into Ophiu-chus on the 3rd. The planet’s motion slows to a crawl around midmonth, when it lies 5° north of its ancient rival, 1st-magnitude Antares. Mars then travels mostly south for a few days before reversing course and starting its retrograde (westward) loop. It crosses back into Scorpius on April’s final day when it shines at magnitude –1.4 — more than twice as bright as it was when the month began.

The planet’s added luster in April reflects its shrinking distance from Earth. This also causes a rapid growth in

after it rises. The best views come when the ruddy world lies highest in the south shortly before twilight starts to paint the sky.

A day on Mars lasts 37 minutes longer than one on Earth. So, if you observe at roughly the same time each night, a feature at the center of the martian disk during one observing session will take an extra 37 minutes to reach the same position the next night.

Use 1st-magnitude Regulus as a guide to find this 10th-magnitude comet as it slides southeast through the background stars of Leo.

Satellite events abound April 6/7. In this view, Io and its shadow are in transit while Europa prepares to dip behind Jupiter. A few hours later, Ganymede will transit, and Europa will emerge from the planet’s shadow.

April 25, 3 A.M.Looking south

CENTAURUS

OPHIUCHUS

LIBRA

SAGITTARIUS

SCORPIUS

LUPUS

10°

Antares

Moon

Saturn

Mars

LEO

Denebola

95

May 1

April 1

6

11

1621 26Path of Hebe

N

E

0.5°

The Lion won’t sleep these April nights

A fab four flaunts its stuff

GET DAILY UPDATES ON YOUR NIGHT SKY AT www.Astronomy.com/skythisweek.


When astronomers discovered

the first asteroids 200 years

ago, the objects were hailed

as new planets. Within a cen-

tury, so many of them existed

(more than 400) that they were

demoted to minor planets and

regarded as celestial vermin.

And now they are hot topics

again. NASA’s Dawn spacecraft

currently orbits 1 Ceres, and

both NASA and its Japanese

counterpart have missions

to visit asteroids and return

samples to Earth. (See “New

missions mine asteroid secrets”

on p. 28.)

Moreover, evidence sug-

gests that 6 Hebe could be the

parent body of 40 percent of

the meteorites that fall to Earth.

As luck would have it, Hebe

reached opposition in March

and is now well placed for

viewing. You can find the 10th-

magnitude asteroid in eastern

Leo through a small telescope.

Hebe sits a couple of

degrees from 2nd-magnitude

Denebola, the Lion’s tail star.

Use the chart below to find the

asteroid’s approximate position

and then sketch four or five

stars around that location.

Return to the same spot on the

next clear night to find which

object moved, confirming its

identity as Hebe.

LOCATINGASTEROIDS

Hebe catches the Lion’s tail

This doesn’t make a huge dif-ference in the planet’s appear-ance, but the slow drift adds up. In the course of a week, the central meridian shifts a bit more than 60°, significantly changing the features visible.

At the beginning of April, Sinus Meridiani and Acidalia Planitia are prominent shortly after Mars rises. Syrtis Major, the planet’s most conspicuous dark feature, rotates into view at the end of April’s first week. It lingers into the latter half of the month if you observe shortly before dawn.

It is currently summer in the Red Planet’s northern hemisphere. Can you see rem-nants of the melting north polar cap? Also keep an eye on Syrtis Major and other dark markings looking for changes in size or shading. Early observers thought vegetation or rising sea levels might cause these seasonal changes; astron-omers now suspect windblown dust and sand are the culprits.

Saturn pokes above the horizon about a half-hour after Mars. Although the magnitude 0.3 ringed planet pales in com-parison to Mars, its yellow glow contrasts nicely with the Red Planet’s hue.

Saturn lies in southern Ophiuchus all month. This area receives a visitor April 25 when a waning gibbous Moon

slides past. Our satellite stands north of Mars and Saturn while Antares lies to their south. All four objects appear within a 10°-wide circle.

Although a telescope deliv-ers wonderful views of Jupiter and Mars this month, neither compares with Saturn. In mid-April, the distant world shows a mostly featureless disk measuring 18" across surrounded by a spectacular ring system that spans 40" and tilts 26° to our line of sight. Saturn’s appearance will improve slowly in the coming weeks as it heads toward opposition in early June.

A telescope also reveals a number of moons. You can see the planet’s biggest and bright-est satellite, 8th-magnitude Titan, through any instru-ment. It passes due north of the gas giant April 3 and 19 and due south April 11 and 27. A trio of 10th-magnitude moons — Tethys, Dione, and Rhea — lurk closer to Saturn and will show up through 4-inch scopes.

The same aperture brings in two-faced Iapetus in early April. This moon glows at 10th magnitude when its brighter half points earthward at greatest western elongation April 5. It then stands 9' from

Saturn. It dims by a magnitude by the time it passes 2' north of the planet April 25.

Do you remember why Mercury looks so nice these April evenings? It’s because the ecliptic angles steeply to the western horizon after sunset in early spring. Unfortunately, the opposite holds true in the east before dawn, which renders the remaining planets hard to see in morning twilight.

On April 1, Venus lies a degree or so above the eastern horizon a half-hour before sunrise. At magnitude –3.8, it shines brightly enough to show up if you have a flat horizon and pristine condi-tions. And you might glimpse Neptune at the end of April. It appears 5° high in the east as twilight begins, but its 8th-magnitude glow will be a challenge to see.

The waning gibbous Moon highlights a grand gathering of bright objects the night of April 24/25 when it passes north of Mars, Saturn, and Antares.

A month of slim asteroid pickings features 10th-magnitude Hebe passing a couple of degrees north of Leo’s tail star, 2nd-magnitude Denebola.


Twists and turns

here is a tangled web of magne-tism running across the Milky Way. Although you cannot see it with your eyes, this fundamental force winds through the spiral arms and influences everything from the

formation of stars to the galaxy’s struc-ture. Where does it come from? How does it affect us? Astronomers don’t know, but in recent years they have come to realize how important cosmic magnetism is, and are working to unwind the answers.

On a basic level, humans have had some understanding of natural magnetism since the time of the ancient Greeks. They dis-covered that lodestone placed on a raft in a bowl of water would align in a north-south direction — in other words, with Earth’s magnetic field. In 1865, Scottish scientist James Clerk Maxwell first recog-nized that electricity and magnetism are not separate forces but actually work together, and that light is a form of electro-magnetic radiation. Maxwell presented the world with the first unified field equa-tions, and “Maxwell’s equations” became the bedrock of electromagnetism, as

fundamental for physics as Newton’s laws are to explain gravitation.

Down to EarthWe can’t see magnetic fields the way we see light, but anyone who has played with a compass has basic experience with mea-suring magnetic fields. A compass needle points north because Earth’s interior essentially contains a giant bar magnet, not unlike the one stuck on your refriger-ator but about 10 times weaker and much larger. It exists because Earth’s rotation causes molten iron in its core to move, creating a “dynamo” that generates the magnetic field.

Earth’s magnetic field is important beyond its use as a handy navigational aid. The magnetosphere it creates around the planet shields us from cosmic rays — charged particles from outer space that can damage electronics — and a steady stream of particles from the Sun known as the solar wind. Strong solar outbursts, which are driven by the Sun’s magnetic field, could prove lethal to an astronaut in space, but the magnetosphere ensures they don’t harm us on the ground. The largest effect we see from the solar wind occurs when the magnetosphere channels the charged particles toward the north and south

This powerful but mysterious force

plays a fundamental role in shaping

galactic structure and allowing stars to form. by Yvette Cendes

Untangling the

T

Yvette Cendes is a Ph.D. student in radio

astronomy at the University of Amsterdam.

Follow her on Twitter: @whereisyvette.

The Whirlpool Galaxy (M51) shows distinctive spiral structure despite its ongoing encounter with a companion galaxy. Radio emission contours (above) trace the galaxy’s magnetic fields, which align with the spiral arms. NASA/ESA/S. BECKWITH (STSCI)/THE

HUBBLE HERITAGE TEAM (STSCI/AURA); INSET: R. BECK (MPIFR)/A. FLETCHER (NEWCASTLE UNIVERSITY)

N

S

Magnetic �eld lines

Spin axis

North pole

Magnetic pole


magnetic poles, where they excite atoms and molecules in the upper atmosphere and cause the aurora.

That said, much about Earth’s magnetic field remains a mystery. For one thing, the geologic record tells us that Earth’s magne-tism reverses every few hundred thousand years. The field disappears for a few thou-sand years and then re-establishes itself with the poles facing opposite directions. These flips occur at random intervals; the last full reversal happened about 780,000 years ago. Although no one knows when the next reversal will take place, and we will be powerless to stop it, researchers do know that Earth’s magnetic field has been weakening for thousands of years. For example, the lodestone-in-a-bowl-of-water trick no longer works if you were to try it today because the field is 35 percent weaker than it was a few thousand years ago.

Scientists predict that when the next flip occurs, our planet will be without its protective magnetosphere for a few thou-sand years. This will increase the number of cosmic rays that reach Earth, exacting an unknown toll on our society. Homo

sapiens survived such flips in the prehis-toric past, as have other species, but this is the first time we have to weather a flip armed with electronic devices. The trendy smartphone cases of the future may include cosmic ray shielding.

Out to galaxiesBut planetary fields aren’t the only ones out there. Magnetic fields are present almost everywhere in the universe, and the biggest webs can span entire galaxies. Although these galactic magnetic field lines are only a billionth as strong as a typical fridge magnet, they more than make up for this shortcoming with their vast size. Maxwell’s equations say that the energy in a mag-netic field equals its strength multiplied by its volume, so a significant fraction of a galaxy’s total energy can be tangled in its magnetic field. “Just like how right now we’re worried about dark matter or dark energy in astronomy, we should also be concerned about magnetism,” says Bryan Gaensler, director of the Dunlap Institute at the University of Toronto, who special-izes in understanding magnetic fields. He adds that the strength of a galaxy’s mag-netic field is equivalent to the radiation pressure exerted by all the stars within it.

Unlike observing the light from stars, however, detecting magnetic field lines in space is tricky because you can’t see them directly except under special circum-stances. This means astronomers rely on various indirect methods, studying how magnetism changes the light that arrives on Earth. “It’s similar to wanting to clean the dirt off a window,” says Gaensler. “If you want to see the dirt, you can’t do it at

are present almost

everywhere in theuniverse, and the

biggest webs canspan entire

galaxies.

Auroral displays occur when Earth’s magnetic field funnels charged solar particles toward the polar regions, where they excite atmospheric gases and cause them to glow. ALLEN HWANG

Earth’s magnetic field behaves like a giant bar magnet. The movement of molten iron in the core generates the field, and field lines loop between the two magnetic poles. The axis of our planet’s magnetic field tilts about 11° to the spin axis. ASTRONOMY: ROEN KELLY


night, but you can during the day by using the light from the Sun.”

This astronomical “window cleaning” relies on a special property observed in starlight called polarization, which shows itself as a particular orientation of light’s electromagnetic waves. Although most light from natural sources is not polarized, astronomers discovered in the 1940s that polarization does cause a “twist” in star-light. They realized that the light becomes polarized on its way to their telescopes, and the culprit is the otherwise unseen mag-netic fields between Earth and the stars.

Scientists use radio telescopes to mea-sure polarization across the sky, mapping what the magnetic structures look like both in our galaxy and in others. It’s a notoriously difficult task. “We have to fight with the sensitivity of telescopes,” explains Rainer Beck, an astronomer at the Max Planck Institute for Radio Astronomy in

Bonn, Germany, who has spent his career mapping magnetic structures in galaxies. He credits his involvement in this field to timing — he started his Ph.D. studies in the 1970s just as the first big radio tele-scopes were coming online. “There was also a lot of trouble in the beginning because people didn’t believe magnetic fields were important,” Beck recalls, “but that’s not true anymore.”

Since then, a startling picture of galactic magnetic structure has begun to emerge. For one thing, almost all galaxies with magnetic fields do not show a tangled

web but instead present an ordered spiral structure — even in galaxies that don’t look spiral-shaped to our eyes. Magnets are fragile things — you can break one by dropping it a few times, for example — so the idea that ordered magnetic structures are so prevalent in our chaotic universe confuses those who want to know where they come from and how they persist.

The birth of starsWhat’s more, it appears that these mag-netic structures affect a wide range of properties in their host galaxies, from overall galactic structure to how stars form within them. The nearby Whirlpool Galaxy (M51) provides a good example. As amateurs with even modest telescopes can see, the Whirlpool has a smaller com-panion galaxy (NGC 5195) that seems to bob on the end of one of M51’s spiral arms like a Christmas ornament. The interac-tion between these two galaxies causes density waves — waves of compression that sweep through a galaxy’s disk — to ripple through the Whirlpool. In this case, the magnetic fields not only follow the optical spiral structure but also compress the gas at the inner edges of the arms.

This is exciting because it appears that the strength of the galaxy’s magnetic field correlates with the density of interstellar gas, though astronomers have yet to pin

A dark dust lane splits the disk of edge-on spiral galaxy NGC 891. The galaxy’s magnetic field (straight lines, inset) close to the disk runs nearly parallel to the plane but forms an X-shaped structure in the halo. ADAM BLOCK/NOAO/AURA/NSF;

INSET: M. KRAUSE (MPIFR)/CFHT/COELUM

The Milky Way’s magnetic field paints a pretty picture in this all-sky view captured by the Planck sat-ellite. Fields thread interstellar clouds and cause the light scattered by dust particles to be polarized (vibrate in a certain direction). Bluer regions indicate stronger polarization while striations reveal the magnetic field’s direction. ESA/PLANCK COLLABORATION

Aurorae circle the South Pole in this view from NASA’s IMAGE spacecraft taken January 7, 2005. This oval and a northern counterpart typically occur 10° to 20° from the magnetic poles. NASA


down the exact details. They do know, however, that cosmic magnetism plays a big role in creating stars born inside these dense interstellar clouds. In the first step, gas begins to clump together in what scien-tists call a protostar. Eventually, the proto-star grows dense enough that it collapses under its own gravity, becoming a full-fledged star when it starts fusing hydrogen into helium in its core. But explaining stel-lar birth through gravity alone is impos-sible. If that were the only force at play, the protostar would spin itself apart long before it could reach a mass approaching that of our Sun. Astronomers now think that strong magnetic fields in these gas clouds create a drag on the protostar, allowing it to gain enough mass to ignite.

While we are used to the classical pic-ture where gravity is the master of the uni-verse, it is apparent that magnetism has been a vital assistant in creating the cos-mos we see today. The Milky Way is a typ-ical spiral galaxy with a spherical bulge surrounded by a flatter pancake of spiral arms some 150,000 light-years across but only 1,000 light-years thick. And though gravity holds it all together, if that force acted alone, our galaxy would deflate because all the matter in the pancake-shaped disk would collapse to the plane. Astronomers think this doesn’t happen because magnetic pressure provides a buoyant force that counters gravity.

Although astronomers have made strides in understanding cosmic magnetic fields, many mysteries remain. One of the biggest is what creates them in the first place. Many researchers think some sort of dynamo mechanism is at play, akin to

how Earth produces its magnetic field. But they argue over how long the fields take to form and how rapidly they gain strength. Astronomers have observed magnetic fields in galaxies much younger than our own, however, indicating the fields already existed in the early universe.

Gaensler belongs to the camp that thinks the formation process could be quick. A decade ago, he led a team that studied polarized light from the Large Magellanic Cloud (LMC), one of the Milky Way’s small satellite galaxies. Our galaxy’s powerful gravity is slowly pulling the LMC apart. This has thrown our companion into turmoil, triggering bursts of star formation and supernovae. The researchers expected that these violent events would shred some-thing as delicate as a magnetic field.

Instead, Gaensler and his team were stunned to discover an ordered, smooth magnetic field despite the chaos. “It’s like having a birthday party all day for a bunch of 6-year-olds, and then finding the house neat and tidy after they leave,” Gaensler says. “Some powerful forces must be at work to keep the magnetic fields from becoming tangled and disrupted.” No one knows exactly what this process would be, but the findings suggest that galaxies can generate magnetic fields quickly, perhaps within 100 million years or so.

Beck has uncovered his share of mag-netic mysteries as well. His most recent was the discovery of novel magnetic structures in the nearby galaxy IC 342. This spiral gal-axy lies just outside the Local Group, mak-ing it one of our nearest neighbors. Beck and his team discovered a helical loop of a magnetic field coiled around the galaxy’s

While we are used to the classical

picture where

is the master

of the universe, it is apparent that

magnetism has been a vital assistant in creating the cosmos

we see today.

The Sun’s magnetic field controls the motions of the multimillion-degree gas contained in so-called coronal loops, which can form arches rising up to 300,000 miles (500,000 kilometers) above our star’s visible surface. Solar scientists captured these loops with NASA’s TRACE spacecraft. NASA/GSFC

Magnetic fields help stars form by slowing down their rotations. Without this braking, a contract-ing protostar would spin so fast that it would fly apart. Magnetic fields also help shape jets of gas spurting from infant stars, such as from Herbig-Haro 46/47. ESO/ALMA (ESO/NAOJ/NRAO)/H. ARCE (YALE UNIVERSITY)


largest arm. “If you take a toy spring and pull it apart to a large size, that’s how it would look,” he says. No one had predicted such a structure before, emphasizing just how complex magnetic fields can be.

Back home againBut don’t sell our galaxy short when it comes to magnetic puzzles. Because we live in the Milky Way, scientists can observe the galaxy’s magnetic field in far more detail than they can any other. Astronomers have seen features unique to the Milky Way, but they don’t know if these are truly unusual or just impossible to detect in more distant galaxies. For example, the magnetic fields follow our galaxy’s visible spiral arms as they do in other galaxies, yet in the Milky Way, each arm seems to have its own mag-netic field that is independent of the others. What’s more, the direction of the field can change from arm to arm, pointing one way in one and the opposite way in an adjacent one. If you take two bar magnets and push the same poles together, they repel; no one can explain why we don’t see a similar effect in our galaxy.

It’s clear that the magnetic puzzle is still missing many pieces. As such, Beck and Gaensler are two of the hundreds of scien-tists and engineers involved in building the Square Kilometre Array (SKA), a new radio telescope project that will begin construc-tion in 2018 in South Africa and Australia. SKA will contain up to a million antennas with an effective collecting area of a full square kilometer (0.4 square mile) and will be 50 times more sensitive than any other radio telescope. Radio astronomers expect to see first light in 2020.

When SKA does come online, studying cosmic magnetism will be a key science goal. In one priority, astronomers will seek magnetic signatures in galaxies that are beyond the reach of today’s instruments. Such observations should shed light on what generates these magnetic fields and when they show up in the formation of a galaxy.

A second priority will be to re-examine nearby galaxies and look in much greater detail at how magnetic fields interact with one another. A more comprehensive pic-ture of magnetic fields in galaxies could show how they affect star formation and galactic structure — and likely will uncover new puzzles as well. Astronomers certainly have made important headway in untan-gling the magnetic universe, but they still have a lot of work to do before these mys-teries are fully unraveled.

Face-on spiral galaxy IC 342 (top) lies some 11 million light-years from Earth, just beyond the Local Group. A map of the galaxy’s magnetism (above) shows most of the field follows the arms, though a helical loop coils around the broad arm to the upper right of the nucleus. TOP: T. A. RECTOR (UNIVERSITY OF ALASKA,

ANCHORAGE)/H. SCHWEIKER (WIYN AND NOAO/AURA/NSF); ABOVE: R. BECK (MPIFR)/NRAO/AUI/NSF/U. KLEIN (AIFA)


AScientists, astronauts, musicians, and the public will come to the Canary Islands this summer for a tribute to the renowned physicist. by David J. Eicher

handful of big science fes-tivals have sprung up over the past decade, and we all know how much they are needed. We now live in a culture that relies on the products of science but in many ways is skeptical or even hostile to it, which

is difficult to understand. Civilization has some progress yet to make. Toward that end, a couple of these festivals are aimed at educational markets. The Starmus Festival,

however, which has taken place twice — in 2011 and 2014 — is unique.

Starmus, whose name comes from stars + music, is the brainchild of astronomer and musician Garik Israelian. A professor at the Institute of Astrophysics in Tenerife, Canary Islands, Spain, Israelian saw his two loves intersect when he became the Ph.D. dissertation adviser for a famous musician in 2006. That year, Brian May, founding member and guitarist of the rock group Queen, reignited work on the astro-physics degree he had abandoned when Queen found worldwide success in 1974.

Israelian struck up a friendship with May as the two collaborated on his degree, which the guitarist earned in 2007 with his study of dust in the solar system’s plane.

Shortly thereafter, Israelian conceived the idea of Starmus, a festival that unites the most important astronomy and allied sciences, along with space explo ration, the arts, and music. It all comes together in a pristine setting: Tenerife and La Palma in the Canary Islands off the northwestern coast of Africa.

The first two Starmus festivals featured a who’s who of astronomy and science

STARMUS 2016

Dark skies and giant telescopes dominate the summit of La Palma, a popular destination for Starmus attend-ees. DANIEL LÓPEZ AND

THE IAC’S PHOTO ARCHIVE


speakers, Sonic Universe concerts featur-ing May and other music icons, and many other events. Starmus 2014 brought in nearly 1,000 people. The next version, planned for June 27–July 2, 2016, is expected to host some 1,800.

At Starmus, you can rub shoulders and talk with the greats — have a glass of wine with Richard Dawkins, chat with Chris Hadfield, and listen to Rusty Schweickart describe what it’s like to sit atop an Apollo rocket as it lifts off. Starmus is an experi-ence like no other in the world of science.

The opening-night dinner at Starmus 2 included good food and conversation, here with radio astronomer Robert Wilson (third from left) and paleoanthropologist Katerina Harvati (right). DAVID J. EICHER


Stephen Hawking — and 12 Nobel Prize laureatesWith the title “Beyond the Horizon: Tribute to Stephen Hawking,” the 2016 incarnation of Starmus will honor one of the leading theoretical physicists of the last century. Hawking’s contributions to relativity theory, black holes, and many astrophysical matters will be a focus of Starmus 3, and he will deliver lectures during the week. For a summary of his life and career, see “The Life and Times of Stephen Hawking” in the January 2016 issue of Astronomy.

At Starmus 2 in September 2014, Hawking delivered two brilliant lectures, the first on the origin and evolution of the cosmos and the second on black holes. They constituted highlights of the week and spawned numerous discussions at din-ner tables and around the conference.

As if Hawking wasn’t enough, 12 Nobel Prize-winning scientists will deliver talks at Starmus 3 on a wide range of subjects.

Astronomers Adam Riess of the Space Telescope Science Institute and Brian Schmidt of the Australian National University will discuss their discovery of dark energy and its consequences for the cosmos. Astronomer Robert Wilson will talk about his discovery in 1964 of the cos-mic microwave background radiation.

Nobel-related lectures will encompass more than astronomy, however. Chemist Eric Betzig of the Howard Hughes Medical Institute will describe his research on super-resolved fluorescence microscopy. Biochemist Elizabeth Blackburn of the University of California, San Francisco, and molecular biologist Carol Greider of Johns Hopkins University will describe their findings on chromosomes. Chemist Harold Kroto will talk about his discovery of and later research on buckminsterfuller-ene and his work on nanochemistry.

And more Nobel Prize winners will speak. Neuroscientists Edvard and

May-Britt Moser of the Norwegian Univer-sity of Science and Technology will describe their detection of cells that constitute the brain’s positioning system. Physicist François Englert of the Université libre de Bruxelles will describe his discovery of the Higgs mechanism along with Peter Higgs. Fellow physicist David Gross of the Kavli Institute for Theoretical Physics in Cali-fornia will describe his finding of asymp-totic freedom in particle physics. And economist Joseph Stiglitz of Columbia University will discuss his work.

And those are merely the Nobel Prize winners! Also speaking will be May, who in 2014 delivered a presentation on stereo imaging in astronomy, one of his favorite subjects. Legendary cosmonaut Alexei Leonov, the first human to walk in space, will talk to the crowd. And so will evolu-tionary biologist Richard Dawkins, who spoke at Starmus 2 about whether aliens on other worlds might resemble humans.

STEVEN BALBUS

ERIC BETZIG

ELIZABETH BLACKBURN

BRIAN COX

RICHARD DAWKINS

FRANÇOIS ENGLERT

STARMUS SPEAKERS

Dusk settles in on Mount Teide on Tenerife dur-ing Starmus 2 in September 2014. DAVID J. EICHER


Moreover, astronaut-explorers will regale the audience with tales of their space flights and the meaning of it all down here on Earth. They will include Apollo astronaut Schweickart, Canadian space guitarist Chris Hadfield, Spanish-American astronaut Michael López-Alegría, American astronaut Garrett Reisman, and Russian cosmonaut Sergey Alexandrovich Volkov.

Still more headlining astronomers will entertain the Starmus crowd. Neil deGrasse Tyson, science popularizer and director of the Rose Center for Earth and Space in New York, will describe his amazing expe-riences as host of the TV series Cosmos. California Institute of Technology’s Kip Thorne will speak on black holes and his longtime friendship with Hawking. Astronomer Royal Martin Rees, Lord Rees of Ludlow, also will address the crowd.

And it goes on. SETI pioneer Jill Tarter will describe the ongoing searches for

extraterrestrial intelligence. Robert Wil-liams will discuss his work on astrophysics over a spectacular career. South African-Canadian physicist Neil Turok will lecture on cosmology and the idea that we may live in a cyclic universe. Brian Cox, physicist at the University of Manchester and popular BBC TV presenter, will describe his amaz-ing adventures in explaining the cosmos.

And astronomer Steven Balbus, chair of the department at the University of Oxford, will explain his work on fluid dynamics, accretion disks, and the Sun.

On top of this incredible list of names, Israelian has not yet announced the Star-mus 3 keynote speaker!

A world-class skyStarmus is a laid-back gathering designed for the maximum enjoyment of the attend-ees — “delegates” as Israelian calls them. Little happens in the mornings and early afternoons, but the schedule is packed from midafternoon into late evening. This allows guests to rest and enjoy the islands in the morning and to observe the universe (as well as visit with celebrities and friends) at night. The Canaries are a near-exact ana-log to Hawaii; the archipelago that makes up the islands, created volcanically, forms a magnificent setting for amazing beaches and extraordinarily dark and steady skies.

CAROL GREIDER

DAVID GROSS

CHRIS HADFIELD

STEPHEN HAWKING

HAROLD KROTO

ALEXEI LEONOV

The Gran Telescopio Canarias forms the centerpiece of European astronomy in the Northern Hemisphere from its perch on La Palma. DAVID J. EICHER

The stage is set for Stephen Hawking to deliver another scintillating talk at Starmus 2. The 2016 edition of the festival is a tribute to the theoreti-cal physicist. DAVID J. EICHER

ALL PHOTOS COURTESY OF THE INDIVIDUAL SUBJECT EXCEPT FOR DAWKINS, HAWKING, AND LEONOV: STARMUS/MAX ALEXANDER


And the near-perfect setting for astron-omy has not gone unnoticed by profes-sional astronomers. The world’s largest single-mirror optical telescope stands on the summit of La Palma. The 10.4-meter Gran Telescopio Canarias, which edges out the twin Kecks on Hawaii’s Mauna Kea, has been a powerhouse in astronomical research since it saw first light in 2007. It is the centerpiece of the Roque de los Muchachos Observatory, operated by the Institute of Astrophysics in Tenerife, but it is hardly alone. Altogether, 14 telescopes or telescopic arrays stand atop La Palma, including the famous 4.2m William Herschel Telescope, the 3.6m Telescopio Nazionale Galileo, and the 2.5m Isaac Newton Telescope.

Options available during Starmus allow delegates to travel from Tenerife to La Palma — a short flight lasting about 20 minutes — to visit the telescopes. The first two Starmus festivals featured a 108- minute roundtable event with selected speakers discussing the state of astronomy and space exploration underneath the Gran Telescopio. The duration of the event sym-bolized and matched the length of Yuri Gagarin’s first space flight. The event is televised live back to Tenerife for all Starmus delegates. And a formal star party with a battery of telescopes takes place one night underneath the majestically black skies of Tenerife.

I often hear from people who are con-sidering traveling to Starmus, especially those living in the United States, that the costs might be prohibitive. Mind you, expensive VIP packages are available for

those who wish to have a nearly continuous “behind the scenes” experience. But the cost to be a delegate at Starmus is 700 euros (350 for Canary Islands residents and stu-dents). That’s about $750 U.S. for normal adult admission. This includes entrance to all sessions, coffee breaks, congress docu-ments, and the Sonic Universe Concert.

Hotels are available in several options and prices are quite reasonable. Flights are, too: Because the Canaries are the equiva-lent of Hawaii to many Europeans, flights from London or Madrid are in the range of $150 or so round-trip. You can travel to Heathrow or Madrid from the United States, “take a right turn,” and head to the Canaries far more easily and cheaply than you might think.

Sonic Universe Concert — and moreMarking Starmus’ last day is an incredible, seismic-scale rock ’n’ roll show put on by May and friends, and this celebrates part of what Starmus is all about: not only intellec-tual realization of our place in the universe, but having a great time within it, too.

In 2011, the Sonic Universe Concert featured May and Edgar Froese along with Tangerine Dream. In 2014, the show con-sisted of Rick Wakeman — arguably the greatest rock keyboardist in history — and his band, who were joined onstage by May for a few songs. Starmus 3 will feature a third-generation Sonic Universe Concert featuring May, Wakeman, Peter Gabriel, and possibly others.

If you love astronomy and music, this is an event you do not want to miss. Trust me — my wife, Lynda, and I sat between Hawking and his nurses on one side and Apollo 16 astronaut Charlie Duke and his wife on the other during the 2014 concert. With May sitting on the stage just 15 feet in front of us, belting out the Queen song “’39,” that sci-fi exploration of relativistic space travel, we all had chills.

I also want to let you know about the richly illustrated book, Starmus: 50 Years of Man in Space (224 pp., hardcover, Canopus Publishing Ltd., London, 2014; ISBN 978–1–62795–026–8, $40). This work, by Editors-in-Chief Israelian and

BRIAN MAY

EDVARD MOSER

MAY-BRITT MOSER

MARTIN REES

ADAM RIESS

BRIAN SCHMIDT

STARMUS SPEAKERS

David J. Eicher is Editor of Astronomy, a mem-

ber of the board of directors of Starmus, editor of

Starmus: 50 Years of Man in Space, and editor-

in-chief of the Asteroid Day project. He looks

forward to seeing you in the Canaries in 2016.

Starmus founder and director Garik Israelian (standing) talks with Glenn Smith of Sky-Skan, Inc. at the 2014 Starmus Festival. DAVID J. EICHER

The massive Gran Telescopio Canarias has a 10.4-meter mirror, making it the world’s largest optical telescope. DAVID J. EICHER


May with me acting as executive editor, contains the complete talks and numerous photographs and illustrations from the first Starmus Festival in 2011. It is really a treasure-trove of entertaining reading. The book contains recollections of space mis-sions from Neil Armstrong, Buzz Aldrin, Leonov, Jim Lovell, Bill Anders, Duke, Claude Nicollier, and others.

But Starmus: 50 Years of Man in Space is not limited to space flight. Incredible talks on astronomy and astrophysics are also present, including ones on what humans are doing in space by May, evolution and exobiology by Dawkins, the origin of life on Earth by Jack Szostak, civilizations in the cosmos by Tarter, breakthrough dis-coveries of the past 50 years by Williams, black holes by Thorne, exoplanets by Michel Mayor, and many others. It is simply an incredible keepsake book!

And there’s another related event that has cropped up this past year that will become a part of Starmus. On June 30, 2015, astronomers celebrated Asteroid Day, a day to reflect on the work that needs to be done to catalog and study near-Earth aster-oids that could threaten our planet. As we all know, an asteroid struck the Yucatán Peninsula 66 million years ago, igniting a firestorm that quickly killed off the dino-saurs and a significant fraction of other life on Earth. Similar events undoubtedly will happen in the future. Asteroid Day is held June 30 to commemorate the date of the Tunguska event in 1908, when a small asteroid airburst flattened a huge area of Siberian forest.

At Starmus 2 in 2014, filmmaker Grigorij Richters concocted the idea of Asteroid Day along with his friend, pho-tographer Max Alexander, and May. Planetary scientists already know of more than 12,000 near-Earth asteroids, but numerous others await discovery. The

second annual Asteroid Day event will be part of Starmus 3, occurring on the fourth day of the festival. For more on Asteroid Day, visit www.asteroidday.org. For a back-ground story on Asteroid Day and the dan-gers asteroids pose, see www.astronomy.com/bonus/asteroidday.

See you in the CanariesStarmus 3 will be an event like no other before it. The celebration of Hawking’s

brilliant life and career will be the center-piece of the week. And that’s just the begin-ning. For complete and updated informa-tion on Starmus, go to www.starmus.com. And for immediate booking information, see www.starmus.com/book-now/.

Trust me — if you come to Starmus, you will thank yourself a thousand times over. It is a life-changing experience, and one that will reset your view of celebrating the universe here on Earth.

RUSTY SCHWEICKART

JOSEPH STIGLITZ

KIP THORNE

NEIL TUROK

NEIL DEGRASSE TYSON

ROBERT WILSON

The 4.2-meter William Herschel Telescope on La Palma — the third-largest optical scope at the time of its first light in 1987 — basks in the setting Sun in this composite image. NIK SZYMANEK AND IAN KING/ING

ALL PHOTOS COURTESY OF THE INDIVIDUAL SUBJECT EXCEPT FOR MAY, THORNE, AND WILSON: STARMUS/MAX ALEXANDER

Longtime photographer Christopher Go takes you step by step through the process of imaging this gas giant.

ASTROIMAGING

esides Earth, Jupiter is the easiest planet to capture photographically. Its high surface

brightness and large angular diameter make detailed imaging accessible to any telescope

size. Even a small scope can resolve major features, like the Great Red Spot.

And now’s a great time to start shooting the gas giant because it lies high in the sky.

Professional astronomers at the Jet Propulsion Laboratory are requesting amateur images to sup-

port the Juno spacecraft, which will arrive at Jupiter in July.

As someone who has been imaging Jupiter for a decade, I’ve seen and tried a lot of equipment

and many processing techniques. Because I have “been there, done that,” the tips and techniques

I’ve developed can help you get started the right way. Take it slow, be sure you understand an idea

before you move to the next one, join an online imaging forum, ask lots of questions, and then

head out and shoot!

B

The author took this image of Jupiter on March 5, 2015, at 12h54m UT. It shows the main equatorial belts, the Great Red Spot, and a whole lot more detail. ALL IMAGES:

CHRISTOPHER GO


Lucky imagingCurrently, the method I and most other amateurs use to capture planets is called “lucky imaging.” This uses a small video camera attached to a telescope. You later process the video with software that lets you stack frames. The program has a routine to perform a check on each frame. It then arranges them in order of quality, letting you stack the best ones to pro-duce a final image.

Which camera?One of the most common ques-tions people ask is whether to get a monochrome or color camera. Color cameras are easy to use and less expensive overall because you don’t need additional accessories like fil-ters and filter wheels.

For beginners I always rec-ommend a color camera. And I have one other tip: When your target planet lies below an alti-tude of 70°, use an atmos-pheric dispersion corrector to offset the effects thicker layers of air have on images.

For the highest-quality images, amateur astronomers should use monochrome cam-eras because their pixels lie closer together than those in color cameras. Monochrome models also are more sensitive.

I use a Celestron Skyris 236M (pictured at lower right) for my monochrome imaging and the Celestron NexImage 5 for my color images.

Telescope and mountAlmost any telescope can pro-duce decent images of Jupiter. That said, use the largest aper-ture you can. Long-focal-length telescopes are ideal for imag-ing Jupiter because they offer higher magnifications.

An optical tube is only as good as its mount, however. As much as it is up to you, choose a sturdy polar-aligned mount.

This necessity (I think it’s more than an accessory) will make your imaging easier.

Other accessoriesIf you select a monochrome camera, you’ll need a filter wheel with a red, green, and blue (RGB) filter set to produce color images. Beyond standard color shots, I often use a meth-ane-band filter, an ultraviolet filter, and an infrared filter. Each of these reveals different layers in Jupiter’s atmosphere. Note that the images you’ll get through these filters will not be as pleasing to the eye as your color shots.

I also suggest a motorized focuser. This accessory will allow fine focus, which is nec-essary to get the best image.

You also may want to use a Barlow lens to increase image size, but I can’t tell you which one exactly. Its magnification depends on the focal ratio of the scope, the pixel size of the camera, and your typical seeing conditions (how steady the air above your imaging site is). A variable Barlow, like the Astro-Physics Advanced Convertible Barlow, allows flexibility.

Imaging preparationThe most important step before you start to image is to make sure that the telescope is at ambient temperature. A telescope warmer than its surroundings will cause tube currents that negatively affect image quality. Also, avoid imaging close to asphalt that’s been in the Sun all day, a hot roof, or other such structures.

FOR THE

HIGHEST-QUALITY

IMAGES, AMATEUR

ASTRONOMERS

SHOULD USE

MONOCHROME

CAMERAS

BECAUSE THEIR

PIXELS LIE CLOSER

TOGETHER THAN

THOSE IN A COLOR

CAMERA.

This image of the giant planet, which

the author captured April 9, 2015, at 10h59m UT, shows great detail and accurate color. The Great Red Spot at the left edge is just starting to rotate into view.

If you use a mono-chrome camera to

shoot Jupiter, you have to capture exposures through red, green, and blue filters to produce a color image.

Christopher Go has produced images of Jupiter nearly every clear night

for a decade from Cebu, Philippines. Contact him at [email protected].


The most important factor in getting the best image is see-ing. This means the site you choose for capturing data is critical. If possible, try to image for three or four days straight from several locations, then pick the one with the highest-quality air. Selecting a site

FireCapture’s con-trol screen offers

numerous options for processing planetary images.

Many planetary imagers cut their

teeth on Registax, which came onto the amateur astronomy scene in May 2002.

If you use the “Wavelet” area in

Registax carefully, your images will dramatically improve.

based on seeing is far more important than selecting a dark site. After all, Jupiter usually ranks as the fourth-brightest object in the sky.

Image captureFireCapture is currently the standard image-capture soft-

ware. It supports different camera manufacturers and controls ASCOM (short for AStronomy Common Object Model) compliant mounts, filter wheels, and focus-ers. Also important to some people: This software is free. Here are some tips on using FireCapture:

1. In “Capture Settings,” make sure that the file name includes the object’s name, the date, and the Universal Time. Also, synchronize your com-puter’s clock with an atomic clock. When doing mono-chrome imaging, make sure you indicate the filter used.

2. Use “Region of Interest” (ROI) to reduce the capture frame size. Using ROI creates smaller files, increases the maximum frame rate, and

makes processing faster. You can do ROI by hold-pressing your mouse’s left button and outlining the area around Jupiter. Make sure you leave some space for inaccuracies in your mount’s drive.

Gain and exposure time controls

Exposure time limit

Histogram should be 80-90% by adjusting gain and exposure time.


3. Set a time limit for cap-turing Jupiter. This is the “Limit” button on the control panel of FireCapture. Because of the planet’s fast rotation, there are constraints on how long an exposure can be for each frame. For apertures smaller than 8 inches, the length is around 60 seconds; 40 seconds for an 11-inch; and 30 seconds for a 14-inch scope.

4. Two controls affect the brightness of Jupiter. These are “Gain” and “Exposure Time.” A higher gain brightens Jupiter but will produce a grainy image. Faster exposure times would allow faster frame rates, but they will dim the object.

Use the image’s histogram as a guide for these two set-tings. When imaging Jupiter, the histogram should peak at around 80 to 90 percent.

One other thing to remem-ber is that the frame rate func-tions as the inverse of the exposure time. I recommend exposure times for Jupiter between 1⁄50- and ⅛0-second, then setting the gain to achieve the recommended histogram. But this is not a hard rule. Exposure times will depend on your seeing.

5. When imaging using the narrowband methane or ultra-violet filters, bin your images at 2x2. This technique allows the camera to use four pixels (in a 2x2 matrix) as though they were a single pixel. Exposure times for these filters vary from 0.25 second to 2 seconds.

StackingStacking software sorts video frames by quality. You then choose how many frames to stack for your final image. I recommend AutoStakkert!2 (AS!2). One nice feature is its ability to do batch processing by opening multiple files for stacking. Beginners find AS!2 easy to use. Here are the steps:

1. Open the file.2. Press the “Place AP on

Grid” button. I recommend alignment point (AP) sizes of

50 or 100 depending on the size of the image.

3. In the “Stack Options” section, use percentage for the amount of image you want to stack. When the seeing is good use 70 to 80 percent. For bad seeing, use 50 to 60 percent.

I normally use 1.5x drizzle for most of my images to increase their size. Test different drizzle settings, and find out which works best for your con-ditions and setup. AS!2 will save the resulting stacked images in a folder automatically.

Wavelet sharpeningRegistax was early stacking software that started the ama-teur planetary imaging revolu-tion. Its most powerful tool is the wavelet-sharpening func-tion, which I highly recom-mend. Here are some tips for using wavelet:

1. The “Layer” sliders con-trol sharpening. Slider 1 is for fine sharpening, and it gets coarser as the slider number increases. I normally use only sliders 1, 2, and 3 and leave sliders 4 through 6 set at 1.0.

Larger images require higher slider values. Don’t push too much or you will introduce more grain in the image.

2. Increasing the value of the “Initial Layer” and the “Step Increment” will help sharpen your image. Test dif-ferent settings to see which works best with your setup. Then save them when you find the sweet spot.

Color combineColor camera users can skip this step. Image processing

To derotate an image of the giant planet,

first open the “Image Measurement” window in WinJupos.

The second step is to open the “De-rotation

of images” window.

Align wire frame to image using F11.

Enter Universal Time as accurately as possible.

Load Image Measurement files

Reduce LD value to reduce edge artifacts

Start derotation


software like Photoshop and Gimp can be used to align colors. Note: Apply wavelets before you color combine. Here’s how to combine colors in Photoshop:

1. Open the wavelet-pro-cessed files.

2. Convert the images into gray scale (“Image,” then “Mode,” then “Grayscale”)

3. Next, at the “Channels” windows, use the “Merge Channels” function, and use the “RGB Color” option. Make sure each file corresponds to the correct color channel.

4. Use the “Move” tool to do alignment adjustment. I suggest you align the Red and Blue channels to the Green channel. Save your color image using the Green filter time.

DerotationThe fast rotation of Jupiter limits the exposure time. Fortunately, WinJupos software has added a feature called “De-rotation,” which allows exposure times beyond what was possible with a single image. Now, you can capture and derotate multiple image sets into an image, which will produce less noise than a single image.

For color, you capture mul-tiple consecutive images. But for monochrome, you must

capture three sets (R, G, and B) of sequences. Do not do con-secutive captures with the same filter, or the resulting image will have red and blue edges. You have to do an RGB set.

When seeing is good, three or four image sets are suffi-cient, but when atmospheric conditions are bad, capture more image sets. De-rotation is a two-stage process.

STAGE 1:

1. Under “Recording,” open the “Image Measurement” window.

2. Load the image. Enter the median observation time. For color images, this is the time on the file name plus half of your exposure time. For mono-chrome images, this should be the green start time plus half the time you exposed on one channel. Make sure you enter the time accurately.

3. Press F11 to automatically align the wire frame to the image. If there seems to be some offset on the auto-align, use the arrow keys to adjust the X and Y positions, the “N” and “P” keys to adjust rotation, and “Page Up” and “Page Down” to adjust the size of the wire frame. Save the image measure-ment. Repeat these procedures for the image set.

STAGE 2:

1. Open the “De-rotation of Images” window under “Tools.”

2. Load the Image Meas-urement (*.ims) files that you made in Stage 1.

3. Choose the output file type and orientation preference.

4. Compile the image. Your

result will carry the midtime of the component images.

Final processingUsing image-processing soft-ware, apply slight unsharp masking to improve the image. Some useful tools in Photoshop are the “Despeckle” and the “Dust and Scratches” filters, which remove noise and grain. You’ll find them in the “Filters,” then “Noise” menus.

Impact detectionSince June 2010, amateur imag-ers have detected four impact events. In response, program-mers developed Jupiter Impact Detection (JID) software to search for them automatically.

So be sure to run all of your captured video streams through JID. Who knows? You might get lucky and achieve your 15 minutes of fame.

Support researchFinally, you can help the cause of science by uploading your images to the Jupiter section of the Association of Lunar and Planetary Observers, the International Outer Planets Watch website, and the JPL Juno support website. This will allow professionals to use your images to give us all a better understanding of Jupiter.

When submitting images, include the date and time of capture, name of imager and location, and the three central meridian system timings of Jupiter. You’ll find them in WinJupos under “Tools,” then “Ephemerides.”

WHEN SEEING

IS GOOD, THREE

OR FOUR

IMAGE SETS

ARE SUFFICIENT,

BUT WHEN

CONDITIONS

ARE BAD,

CAPTURE MORE

IMAGE SETS.

On June 3, 2010, the author imaged

an impact scar (arrow) in Jupiter’s atmosphere discovered by Australian amateur astronomer Anthony Wesley.

MEET THE AUTHOR

Imaging wizardChristopher Go has sent an astounding 977

sets of images of Jupiter to Astronomy maga-

zine, starting in early 2007, and he carefully

processes each shot before sending it. This

amount of work alone places him in the top

tier of planetary imagers. Recently, he began

teaching others how to image Jupiter. Christopher Go

CO

UR

TE

SY

CE

LE

ST

RO

N


Today’s trends will lead our hobby to a better and more popular future.

text by Kevin Ritschel and

Maria Grusauskas;

illustrations by

Kellie Jaeger

Where is amateur astronomy heading?

A LOOK AHEAD

OPTICAL ASTRONOMY

has changed greatly since the days Galileo first glimpsed Jupiter’s four largest moons or confirmed the phases of Venus through a simple telescope. As technology continues to revolutionize our cherished hobby with computer-controlled telescopes and CCD cameras, the intrigue of the cosmos retains its primitive pull on mankind.

As long as there are pockets of dark sky anywhere around the world, the future of the hobby will be bright. We even go as far as to say that professional and amateur astronomy are coming into a golden age. From state-of-the-art innovations already here (or coming soon to a telescope near you) to space com-mercialization, these seven trends will shape the future of astronomy as we know it.


1. Compelling subject matter — the overwhelmingly powerful growth driverAstronomy is inherently amazing and of profound interest to most people. Space, with all the objects it contains, is big and wonderful. Driven by curiosity, astronomy is like the lyrics in a Taylor Swift song: It “never goes out of style.”

But interest in astronomy is erratic. A lot of noise and many earthly concerns consume modern society. Transient hap-penings such as well-positioned eclipses, bright comets, spectacular meteor storms, and favorable conjunctions create tempo-rary crescendos of interest and keep tele-scope users (and retailers) busy during these universal special events.

Scott Roberts at Explore Scientific notes that, “over the last four centuries of ama-teur astronomy, there have been many times when this community has receded and swelled in numbers, and I see no rea-son why it will not continue to do so.”

The current pace of astronomical dis-covery by the Hubble Space Telescope, New Horizons, and others — and all of the esti-mated $3 billion worth of free publicity they provide — will continue to foster fas-cination in astronomy. And such a growing interest in astronomy has encouraged pri-vate companies to enter the space industry.

2. Social astronomy — millions of advocatesManufacturers and dealers imported more than 2 million telescopes into the United States in 2014, according to import data from the U.S. Department of Commerce.

That’s a lot of telescopes. Over the last five years, this number has varied by only 6 percent. In other words, more than 10 mil-lion telescopes have been brought into the United States since the start of the decade.

So where are they? The same Commerce data offers a clue, showing an average cost of about $41 per unit. This means a lot of these were low-cost beginner scopes (“toys” to the more serious hobbyists).

While some percentage of these con-sumers must develop a devotion to the sky, we can assume, fairly safely, that many of these low-cost scopes are decorating man caves while the rest are gathering dust in garages, basements, and closets — their buyers unable to make them work or disap-pointed in their first views. It’s both an opportunity and a challenge to entice these first-time telescope buyers to get more involved in the hobby.

The future of gaining more engaged hobbyists, however, may depend on social media — from tweets to Facebook pages to citizen science. Astronomy is apolitical; it appeals across generations and ethnicities to all human beings, and it is just down-right wonderful (if not sometimes unbe-lievable) to the average person. And anyone can step outside on a clear night to see some aspect of our universe and share in a common, global experience, which makes it the perfect topic for social media.

From astrophotographs and observing reports to opinions, predictions, and live virtual star parties, the free and ubiquitous channels of social media are a hotbed for sharing astronomy-related material and will facilitate growth in the hobby. Social media momentum could propel even more people to seek college or adult-education level courses in the topic or acquire a telescope and start exploring the night sky.

3. Increased computational power and connectivityTelescopes and their accessories (like eyepieces, finder scopes, and computer databases) are going to get even better as computational power gets cheaper and integrated into more devices (the holy grail being the Internet of Things). With more computational power will come better opti-cal designs for every element in the optical train from objectives to eyepieces.

Designs such as the ultrawide eyepiece and fast (short-focal ratio), corrected (no optical aberrations) Newtonian reflectors and astrographs (scopes designed for astro-imaging) that have revolutionized deep-sky observing and imaging will not stop amaz-ing us or tempting us to open our wallets. Indeed, the folks at the telescope manufac-turer Levenhuk predict that people will demand “perfect” (aberration-free) tele-scopes and that technology will happily honor that demand by supplying better and better designs.

Better, affordable computational power will impact how telescopes work and how we use them. More of the difficult aspects of telescope operation, such as alignment, tracking, and guiding, will be available as an app on a smartphone. Pedro Pereira, a product manager at the German telescope company Nemax, predicts that the average astronomer will someday have apps that allow them to completely operate a tele-scope — polar align (if needed), locate and inform about objects, and track and image objects in the sky — essentially in real time, right on their smartphones. Some amateurs in the future won’t have to use an eyepiece, they can look at the sky on their touchscreens. We’ll let you start the debate on whether this is good or bad.

Kevin Ritschel has a lifelong interest in astron-

omy and has headed product development and

marketing functions within the telescope indus-

try. Maria Grusauskas is the Community Editor

at Orion Telescopes & Binoculars and a freelance

writer in Santa Cruz, California.


4. Bigger and smaller telescopesTelescopes are going to get bigger — and smaller, too. Serious deep-sky observ-ers will always push the limit toward larger “portable” telescopes. The largest commercial “amateur” telescope we are aware of is a 50-inch monster Dobsonian-mounted Newtonian reflector at the Deepsky Astronomical Research Center Observatory in California. That said, rumors of an 80-inch-plus reflector being built by the same supplier — Normand Fullum of Optiques Fullum in Canada — recently surfaced. Such is the nature of serious enthusiasts.

But many people in the United States are moving toward smaller homes and cars. If you look at hobbyists in Japan, where homes and cars are much smaller on average, you’ll see a plethora of small, eas-ily deployed telescopes that fit into apart-ments and automobile trunks awaiting trips to dark skies. We predict that smaller, well-designed telescopes that are modular and/or of a compact, lightweight design will appeal to a large segment of hobbyists and will make the hobby easier to enjoy even for beginners.

5. Better cameras (and software)Bryan Cogdell at Celestron summarizes the status and near future of imaging equipment by pointing out the three major drivers: 1) Smartphones, which are great for the Moon and events like the Venus transit of 2012, are today’s social-media imaging device of ease, so telescope mak-ers and app developers are devoting seri-ous time to them; 2) DSLRs, which have replaced most single-shot color cameras developed for astronomy; and 3) special-ized, high-efficiency CCD cameras that excel at imaging celestial objects.

While some argue that there is an over-saturation of vendors for astronomical cameras today (there are a lot of choices), no one is saying that cameras will not con-tinue to improve. Indeed, we hope that more of the processing tasks required to create stunning images will be better inte-grated into the camera’s software to make astroimaging more of a point-and-shoot experience. Imaging chips will continue to advance, but the biggest improvements will be in solutions developed for improved software and hardware integration.

Levenhuk, for example, sees a future where amateurs easily link their telescopes into global networks to share real-time observations of the sky in improved social media venues. Amateurs already can par-

ticipate in viewing the sky through shared telescope images and live broadcasts, including the SLOOH camera and virtual star parties like the one run by Universe Today’s Fraser Cain of Canada.

And don’t forget video! Today’s astro-oriented video cameras can make great “video finders,” allow deep-space observers to catch objects too faint for the human eye, and make sharing with a group or social media a breeze. Because video can help pull out faint signals in light-polluted areas, some imagers even advocate it as the future of deep-sky observing.

6. Smart optics and peripheralsBinoculars are a great way to learn the sky. They are perfect tools for beginners and treasured by experienced observers as wide-angle companions to complement a telescope. Will they evolve? We hope so. We look forward to lighter binoculars — and can some vendor please come up with affordable shock-proof binoculars that will

hold their collimation (optical alignment) through shipping and normal handling in the field?

The firms Leica, Zeiss, and Swarovski already offer binoculars that incorporate a laser rangefinder and display range data in the eyepieces. How about a “smart” bin-ocular to help you find objects in the night sky and tell you something about what you are seeing? As the pointing accuracy of smartphones gets better, this may simply be a bracket that attaches binoculars to an astronomy-enabled smart phone.

If a binocular can get smart, why can’t an eyepiece? The technology already exists for an image to appear in the eyepiece with information like object name and location.

Of course, a smart eyepiece, networked with a smartphone, could enhance the types

of social experiences (like real-time discus-sion), guided tours, and education that could occur with networked telescopes. We’d love to see courseware for science classes and budding astronomers released for such smart eyepiece-enabled telescopes. One day, observing could become synony-mous with looking at a smartphone screen using an onboard camera. Indeed, this capability is trivial.

7. Web-based salesDealers are selling more and more tele-scopes via the Internet. It’s usually cheaper and more convenient, if you already know what you want. Unfortunately, fewer and fewer places exist where a new astronomer can go get a real-world introduction that can rapidly put equipment needs and limi-tations into perspective.

Can the astronomy community react effectively and work together to promote the hobby without a local dealer that can demo the basics needed to enjoy the hobby? Can social astronomy, clubs and outreach take up the slack? Time will tell.

Which direction?With so many people buying telescopes of one sort or another, we can quantify one dimension of active interest in the sky in the United States alone. We also think that plenty more armchair astronomers feed their curiosity with web-based news and images, or enjoy simply sitting under the beautiful mystery that a dark sky provides, pondering what it all means.

Through talking with industry experts, we have heard a variety of innovative ideas for improving the hobby — a buzz that promises not just a lively future, but an evolving one, where imaging and observ-ing continue to become easier, more effec-tive, and more fun. We can hardly wait!

hot new scope tested

EQUIPMENT REVIEW

Y ou can’t judge a telescope by its sparkly tube, but the new Sky-Watcher USA Maksutov-Cassegrain 127mm sure looks nice

right out of the box. I’m always excited to try out new equipment, and I’m especially fond of small portable scopes. The reason is simple: I use them more. So when I had a chance to try out this new 5-inch scope, I jumped at it.

DesignThe telescope is a compound Maksutov-Cassegrain hybrid system. Most observers are familiar with the Schmidt-Cassegrain design, like the classic 8-inch Celestron telescope. These scopes are short and com-pact because the light traveling through them reflects several times, which results in a “folded” light path.

In a Schmidt-Cassegrain, light first passes through a

Schmidt corrector plate at the front of the telescope, then to a spherical mirror. In a Mak-Cass design, the front plate has a slight negative curvature, but the mirror is still spherical. The corrector reduces sev-eral problems, including chromatic and spherical aberration.

The first manifests itself as color fringes on bright objects, and the second is a smearing of the focus because a spherical mirror doesn’t focus all the light it collects at one point. If done right, the corrector yields a short, portable telescope that deliv-ers sharp images across the field of view. And if my observations are any indication, the Sky-Watcher USA Maksutov-Cassegrain 127mm is indeed done right.

DetailsSky-Watcher USA is based in Torrance, California. I’ve been aware of its telescopes

for many years and have appreciated the quality the company puts into its products. As I unpacked this tele-scope I first noticed the beautiful deep-blue finish of the tube. It really does sparkle.

Included components are a 6x30 finder scope, a 2" star diagonal, and 28mm

eyepiece. An adapter ring handles 1¼" eye-pieces. A standard dovetail plate is part of the tube assembly. Compared to 5-inch Schmidt-Cassegrain telescopes, this Mak-Cass is a bit longer and just a little bit heaver. This gives the scope a nice, substantial feel.

The telescope came without a mount, but it was not a problem for me; I have a number to choose from. For this test, I put the scope on a German equatorial mount and an alt-azimuth one. Both handled the 5-inch scope without a problem.

Combine 5 inches of light-gathering power with easy portability,

and you have a winner of a scope. by Raymond Shubinski

Under the skyMy first effort at observing with the Sky-Watcher USA 127mm was an early evening scan of the Moon. Our satellite was in a waxing gibbous phase and brighter than I like, but I was struck by the overall crispness of the details I could see through the 28mm eyepiece.

I always enjoy observing double stars. Typically I’ve used refractors for these endeavors. Double stars present a double challenge for the equipment: Can the scope resolve both components, and are the colors true? Naturally, I wanted to see how the Mak-Cass did with this type of object.

The first target was an easy mark, beau-tiful Albireo (Beta [β] Cygni). As expected, the 28mm eyepiece split this famous double with ease. Because the telescope has a focal length of 1,500 millimeters, this eyepiece provides a magnification of 54x, plenty of power for the job.

Through the scope, Albireo’s colors were startling. The primary appeared distinctly yellow, while the secondary was a wonder-ful vivid blue. Also, the sky between the two stars was nice and dark. I watched as Albireo drifted toward the edge of the field of view, looking for any distortion. Even when the stars were on the very rim of the field, I saw none.

Next, I turned to Almach (Gamma [γ] Andromedae). The 1881 edition of A Cycle of Celestial Objects by William Smyth and George Chambers says this star’s two com-ponents are orange and emerald green.


The Mak-Cass 127mm incorpo-rates a 2" focus-er. The company

includes a 1¼" adapter.

The telescope has

a 1,500-millimeter focal length, which

creates an f/12 optical system.

AL

L P

HO

TO

S ASTRONOMY

: W

ILL

IAM

ZU

BA

CK

Through the Sky-Watcher USA scope, the brighter of the two appeared pale yellow while the fainter star looked white with just a hint of blue. This compares well with observations of Almach that I have made with large refractors. I upped the magnifi-cation to 88x by inserting a 17mm Plössl. The two stars remained sharp, and the col-ors held up well.

Although Lyra was low in the west, I turned the scope on the famous Double-Double, Epsilon (ε) Lyrae. Splitting the two main stars was easy. I had to bump up the power, however, to split the two into four. I think the cause lay in the altitude of Lyra and, therefore, the atmosphere.

My next quarry was a favorite: the Andromeda Galaxy (M31). On the night I observed it, the sky was steady and trans-parent. I once again began with the 28mm. This eyepiece provides about a 1° field of view. M31 appeared as an extended oval of distinct nebulosity. The core of the galaxy shone brightly.

As I panned back and forth, I could trace the galactic arms for another degree or so on either side of the nucleus. The contrast between the galaxy and the dark background sky was really great. Because of the outstanding contrast, I had no prob-lem picking out the big spiral’s two com-panion galaxies, M32 and NGC 205.

After a stretch of cloudy nights, I finally had a chance to observe in the early morn-ing hours. My main goal was the beautiful October grouping of Venus, Jupiter, and Mars. Of course, as I started to observe, some winter sky objects sidetracked me.

I quickly surveyed the Orion Nebula (M42). Even against the lights of Las Vegas, I clearly could see the extended wings of the great nebula through the 28mm eye-piece. I then increased the power to resolve the Trapezium. This compact grouping of stars easily resolved into five distinct and sharp objects — yet another testament to the quality of this scope’s optics.

Next, I moved the Mak-Cass to the Pleiades (M45) and reinserted the 28mm. The sky appeared as a dark backdrop, and the cluster’s stars were like Tiffany dia-monds strewn across a black cloth. I stopped on the bright star Alcyone (Eta [η] Tauri) to see if I could detect any chromatic aberration. None was visible.

The eastern sky was still dark, and Venus, Jupiter, and Mars were well above the horizon. I had planned this observing session so I could watch Jupiter’s moon Io emerge from behind the gas giant. The planet’s other three large satellites — Europa, Ganymede, and Callisto — were strung out on one side of Jupiter.

Using the 17mm Plössl eyepiece, I watched as Io began to appear. The

sharp definition provided by the 5-inch Mak-Cass proved itself again. I spotted Io immediately. After just a couple of min-utes, I could see dark space between Io and Jupiter easily. At high power, Io and Europa, which were in the field of view, had discernible disks.

The verdict Sky-Watcher USA’s Maksutov-Cassegrain 127mm is a great little scope for a variety of observing desires. Its long focal length provides sharp, color-free images. The 28mm eyepiece is high quality with great eye relief, which allowed me to keep my glasses on. I’ll be trying some of the other 2" eyepieces in the Sky-Watcher USA line.

More and more, I find myself reaching for a “grab and go” scope. When presented with a clear sky but limited time, conve-nience is important. With the Sky-Watcher USA 127mm, I found no compromise in quality. This is a scope for backyard use or

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Raymond Shubinski has decades of observ-

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Sky-Watcher USA Maksutov-Cassegrain 127mm Aperture: 5 inches (127mm)

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Solis Lacus

Mare

Sirenum

S

N

fp


ASTROSKETCHING B Y E R I K A R I X

The Red PlanetMars may be slipping low in

the sky for observers in the

Northern Hemisphere, but

don’t let that stop you from

observing the Red Planet

while you can. Each sketch

provides a building block of

experience for capturing those

elusive details for which Mars

is notorious. During your

observations, you can expect to

see atmospheric features and

even surface detail. Over time,

observers can follow seasonal

fluctuations and changes in

martian albedo (reflectivity).

In mid-April, Mars

begins retrograde motion in

Ophiuchus and will move

westward against the stars.

The planet slips into Scorpius

on May 22, marking the date

of opposition when Mars is on

the opposite side of Earth from

the Sun. By May 30, it will lie

near the border of Libra for its

closest approach to Earth. Its

apparent diameter will reach

time and date next. A soft

white observing light works

well for planetary sketching,

especially if you’re using col-

ored pencils. Strive to complete

the sketch within about 20

minutes before features rotate

out of view.

Outline the polar caps and

prominent surface details first.

Fill in the darkest and then

the lightest areas next before

blending your sketch with a

clean, soft blending stump.

Working in small sections,

refine your sketch with a pen-

cil by homing in on the finer

details. Finally, use a kneaded

or shaped eraser to draw (by

lifting the graphite) clouds

and haze and to make final

adjustments in tonal variances.

Record the time once more,

and then mark the orientation

(north and east or preceding

[disappearing features] and

following [appearing features])

to complete the sketch.

Questions or comments?

Feel free to contact me at

[email protected].

18.6''. As a bonus, the North

Polar Region is currently tilted

toward Earth so that the clouds

that form over both polar

regions may be visible.

One method to maximize

your view is to use the high-

est magnification that see-

ing (atmospheric steadiness)

allows. Another is to use filters

to increase the sharpness of

martian features. For example,

refer to the set of comparison

sketches provided by Carlos

Hernandez (Image #1). For the

first observation, he used a

Wratten 30, which is a magenta

filter that enhances blue atmo-

spheric and red surface features

while absorbing green hues.

Notice the projections he cap-

tured extending from Solis

Lacus near the preceding limb

and the bright streak within

Mare Sirenum in the southern

hemisphere. A Wratten 38A

(blue) filter worked to highlight

limb haze and clouds in his

second observation.

Sol Robbins used a variable

filter system for his Mars obser-

vation (Image #2). This unit

sports a wheel to adjust the fil-

ter’s color transmission, which

saves time and prevents dis-

tractions caused by swapping

out filters. Note the remarkable

amount of detail he recorded in

a short timespan while using a

3.5-inch refractor.

Study the eyepiece view

before you begin sketching.

Then, create a 2-inch circle on

your paper and draw in the

phase. Record the universal

Image #1. Carlos Hernandez created this pair of Mars sketches Nov. 17, 2005, 30 minutes apart as a filter comparison while using a 9-inch f/13.5 Maksutov-Cassegrain reflector at 248x and 347x. He employed a Wratten 30 (magenta) filter for the first observation (left). For the second observation (right), he used a Wratten 38A (blue) filter. He used Prismacolor colored pencils on white paper for both sketches, then made minor adjustments with Photoshop. South is to the top, and the preceding limb (where features are disappearing) is to the left. CARLOS HERNANDEZ

Image #2. Sol Robbins sketched Mars from 6h00m through 6h12m UT on January 21, 2010, using a 3.5-inch f/10.1 refractor, a 2.5x Barlow lens, and a 10mm Plössl eyepiece for a magnifica-tion of 273x. He used a Sirius Optics Variable Filter System to improve con-trast. He completed the sketch with 4H and 2B pencils on white paper, creating the tones of the martian plains by gen-tly tapping and rolling an eraser. South is to the top, and the preceding limb is to the left. SOL ROBBINS

W W W.ASTRONOMY.COM 67

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Mount + tripodOrion Telescopes & BinocularsWatsonville, CaliforniaOrion’s StarSeeker IV GoTo

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DVD tutorialDamian PeachSelsey, EnglandHigh Resolution Astrophotography

— Part II follows the author’s suc-

cessful first DVD. This one focuses

on processing planetary image

data using Photoshop. The DVD

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Observatory guideSpringer, New YorkBuilding a Roll-Off Roof or Dome

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1000 200 300Input

Output


In this column, I’ll explain an

easy way to quickly increase

contrast in both brightness

and color for objects that lack

distinct features. Several of the

features in Photoshop enhance

contrast in layers that are cop-

ies of themselves. By far the

easiest one to manage is the

“Soft Light” blending mode.

A good case in point is an

object like NGC 488. This

beautiful galaxy has tightly

wound spiral arms with intri-

cate dust lanes and details at

the smallest scales.

It is difficult to see these

features because the contrast is

modest, and the adjustments

necessary to reveal the inner

regions severely flatten the

brightness profile of the galaxy.

Image #1 shows the stage in

processing that I consider

insufficient in contrast.

Several of Photoshop’s

blending modes are conditional

effects based on the grayscale

value of one of the two layers. If

the value is less than 50 percent

gray, one effect occurs, and if

the value is greater than 50

percent gray, you’ll see a differ-

ent effect.

COSMICIMAGING B Y A D A M B L O C K

Soft lightIn the case of “Soft Light,” a

burn effect occurs with pixels

less than 50 percent gray (as

measured from the bottom layer)

and dodging is applied for pixels

brighter than that mark. The

burning that occurs darkens

values less than 50 percent gray

a bit faster than the dodge effect

brightens the brightest values,

and leads to a soft-light feeling.

Image #2 shows the resulting

S-shaped curve I plotted to

illustrate that it certainly is a

contrast-enhancing blending

operation. This curve is typical

of producing contrast in the

outputted values but note that

the bottom left (small grayscale

values) are slightly more

strongly affected.

Image #3 is the result of

blending the original image of

NGC 488 with its copy. Above a

certain threshold, the increase

in contrast is appealing. Faint

pixels and the sky become cata-

strophically clipped. Thus, this

“Soft Light” technique requires

a strongly blurred object mask

that hides all parts of the image

below the minimum brightness

threshold (Image #4, top row,

right). Also note that the “Soft

Light” blend affects the color

values as well. Where darker

colors are chosen, by virtue of

the burn application, a modest

increase in color saturation

occurs. The final result (Image

#5) dramatically shows the

benefits of the technique by

enhancing the contrast of dust

lanes and making the color of

the spiral arms more distinct

and attractive.

This technique is easy to

master. You should apply it to

reasonably clean and high-

signal images at the end stages

of processing. Simply make a

copy of the image in another

layer, blend with “Soft Light,”

and apply the appropriate

object mask. Because this is a

global effect, you won’t invest

much time seeing if it offers an

enhancement you like. Large

diffuse nebulae and face-on

spiral galaxies tend to be good

subjects for this kind of pro-

cessing.

BROWSE THE “COSMIC IMAGING” ARCHIVE AND FIND VIDEO TUTORIALS AT www.Astronomy.com/Block.

Image #1. At the start of processing, this version of NGC 488 had contrast unacceptable to the author. ALL IMAGES: ADAM BLOCK

Image #2. (Below) The author plotted input ver-sus output of grayscale values of the soft blend on a copy of a grayscale tablet. This is a typical contrast curve weighted slightly more toward darker pixels.

Image #5. The author’s final version shows more detail than any previous incarnation. You can view a high- resolution version of this at www.adamblockphotos.com/ngc-488.html.

Image #4. This screenshot from Photoshop shows that the author created a copy of the image and a strongly clipped and blurred object mask.

Image #3. This is the author’s raw blended image of spiral galaxy NGC 488. Improvement already is starting to show.

Soft Light Curve

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READERGALLERY


1. COLORFUL SKY

This stack of images shows many trails of stars in the Northern Hemisphere summer sky. The unusual background color, however, doesn’t come from the stars but rather from an aurora, which was active that night. The peak in the foreground is Mount Rainier. (Nikon D750, 24mm lens at f/1.4, ISO 5000, a stack of two hundred 8-second expo-sures) • Matt Dieterich

2. STELLAR BOOM

The Veil Nebula (NGC 6960/79/92/95) is a huge supernova remnant in Cygnus. It blazed forth as a “new” star in our sky some 15,000 years ago. (5.2-inch Stellarvue SVS-130 refractor at f/5, SBIG STL-11000 CCD camera, four-panel mosaic LRGB image with exposures of 640, 550, 400, and 400 minutes, respectively, combined with six-panel Hydrogen-alpha/Oxygen-III/Sulfur-II image with exposures of 720, 880, and 940 minutes, respectively) • Jon Talbot

1

2


3. RICH FIELD

Face-on spiral galaxy NGC 5364 (top) lies in Virgo with several others in the same field of view. Elliptical NGC 5363 lies below it, and edge-on spiral NGC 5356 is to the lower left. (10-inch Optical Guidance Systems Ritchey-Chrétien reflector, Atik 11000M CCD camera, LRGB image with exposures of 9, 3, 3, and 3 hours, respectively) • Warren A. Keller

4. TRIPLE PLAY

Because the Sun is so bright, imagers can use different filters to display its features. This is a combination through visual, calcium K-line, and Hydrogen-alpha filters. (Three-telescope combi-nation, visual: 2.6-inch Astro-Tech 65 EDQ; calcium: Coronado CaK 70mm; H-alpha: Coronado SolarMax II 60mm double-stacked, Imaging Source DMK 41AU CCD camera. Each image was the best of 1,200 frames generated during video captures taken November 21, 2015) • David Barnett

5. BRIGHT?

Despite the faintness of this nebula, its designation, LBN 603, means it was part of a list of bright nebulae com-piled in 1965 by American astronomer Beverly T. Lynds. (4-inch Takahashi FSQ-106 refractor, SBIG STL-11000 CCD camera, 12 hours of LRGB exposures, stacked) • Robert Fields

6. SIX-SHOOTER

The Winter Hexagon is an asterism that contains the bright stars Aldebaran, Capella, Pollux (some references say Castor), Procyon, Sirius, and Rigel. It appears here above the Manla Reservoir in Tibet. (Canon 6D, Nikkor 14-24mm f/2.8G lens set at 14mm and f/2.8, ISO 6400, 45-second exposure) • Jeff Dai

7. 1,000 POINTS

Globular cluster NGC 288 glows at magnitude 8.1 in Sculptor. This object’s central region has a poor concentra-tion of stars, which actually means you’ll resolve more of them through a medium-size scope. (27-inch corrected Dall-Kirkham reflector, Finger Lakes Instruments CCD camera, RGB image with 20 minutes of exposure through each filter) • Damian Peach

Send your images to: Astronomy Reader Gallery, P. O. Box

1612, Waukesha, WI 53187. Please

include the date and location of the

image and complete photo data:

telescope, camera, filters, and expo-

sures. Submit images by email to

[email protected]

7

3

4 5


Nice to meet youWhen police take a mug shot, they get face-on and profile views to bet-ter capture the person’s essence. In NGC 4298 (left) and NGC 4302, astrono-mers have an equally powerful tool for studying spiral galaxies. A con-spicuous dust lane domi-nates the classic edge-on spiral NGC 4302. The dark clouds block light from the hot, young suns that populate the galaxy’s disk. In its more face-on neighbor, the youthful stars stand out as a bluish swirl. The slight warping in the disks’ outer regions shows that the two objects have started to interact. The pair resides in the Coma-Virgo cluster of galaxies some 55 million light-years from Earth. CANADA-FRANCE-HAWAII TELESCOPE/COELUM

BREAKTHROUGH

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Milky Way imagePhotographer: Charlie WarrenCamera: Canon 60Da6 panel panorama with 4 minute exposures8mm fisheye lens at f/3.5ISO 1600

The Sky-Watcher USA Star Adventurer multi-purpose mount is perfect for anyone — Milky Way photographers, eclipse chasers and all of you

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Compact and portable — weighing only 2.5 pounds — this versatile mount is also powerful. Its quality construction, utilizing

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The Star Adventurer features:

• Multiple preprogrammed speeds perfect for time-lapse photography, wide angle

astrophotography and astronomical tracking

• Tracking selectable between multiple sidereal rates, Solar and Lunar

• Built-in polar scope with illuminator

• DSLR interface for automatic shutter control

• Built-in auto-guiding interface

• Long battery life — up to 11 hours

• External Mini USB power support

• Compatible with 1/4-20 and 3/8 inch camera tripod threads

©20

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SOUTHERNSKY

MARTIN GEORGE describes the solar system’s changing landscape as it appears in Earth’s southern sky.

June 2016: Saturn’s reign of gloryThe evening sky boasts this

month’s three brightest plan-

ets. Farthest to the west is

mighty Jupiter, which lies

due north as darkness falls in

early June. The giant world

shines brilliantly at magnitude

–2.1 and dominates its host

constellation, Leo the Lion.

The planet appears to the

upper right of 1st-magnitude

Regulus, the blue-white star

that marks the handle of Leo’s

Sickle asterism.

Although Jupiter reached

opposition and peak visibility

in March, it remains a fine

sight through any telescope.

View it near the end of twilight

when the planet lies highest

and its light passes through less

of Earth’s atmosphere. Look

for two dark equatorial belts

that sandwich a brighter zone

coinciding with the planet’s

37"-wide equator. Turbulent

features often pop up near the

edges of these bands. The Great

Red Spot — a giant storm near

the southern border of the

South Equatorial Belt — also

shows up if it happens to be

on Jupiter’s Earth-facing hemi-

sphere. You likely will need a

20-centimeter or larger scope

to see it clearly.

Two more planets vie for

attention to Jupiter’s east. Mars

came to opposition in late

May and starts this month as

Jupiter’s near equal. The Red

Planet shines at magnitude

–2.0 among the much fainter

background stars of Libra

the Scales. The world moves

slowly westward relative to

this backdrop during June. As

you watch this so-called retro-

grade motion, think about

the astronomers of long ago

who were puzzled whenever

an outer planet reversed its

normal eastward route. The

great 16th-century astronomer

Nicolas Copernicus finally

figured it out when he deduced

that the Sun lies at the center of

the solar system and the outer

planets appear to back up when

Earth overtakes them on its

smaller and faster orbit.

It’s a wonderful time to

observe Mars through a tele-

scope. The planet appears well

above the horizon once dark-

ness falls and passes nearly

overhead by late evening. Its

disk spans 19" in early June

and shrinks a bit, to 16", by

month’s end. That is plenty

big enough to reveal subtle

surface markings through most

amateur instruments.

Scan approximately 15° to

20° east of Mars and your eyes

will fall on Saturn. The ringed

planet remains in southern

Ophiuchus the Serpent-bearer

all month, some 7° north and

a little east of ruddy Antares

in Scorpius.

Saturn reaches opposition

June 3, which means it lies

opposite the Sun in our sky and

remains visible all night. It also

lies closest to Earth at opposi-

tion, so it shines brightest

(magnitude 0.0) and appears

largest (18" across the equator)

through a telescope. The ring

system spans 42" and tilts 26°

to our line of sight (the highest

tilt at opposition since 2003).

Any scope will show the

Cassini Division, the dark gap

that separates the outer A ring

from the brighter B ring. Also

keep an eye out for Saturn’s

brightest moon, 8th-magnitude

Titan. A 10cm or larger instru-

ment will bring in Tethys,

Dione, and Rhea, a trio of

10th-magnitude moons.

The inner planets don’t fare

as well as their outer cousins.

Venus passes on the far side of

the Sun from our perspective, a

configuration known as supe-

rior conjunction, June 6. It

remains invisible all month.

But Mercury puts on a nice

morning show in early June. It

appears some 10° high in the

east-northeast an hour before

sunrise throughout the month’s

first week. The innermost

planet peaks at greatest elon-

gation June 5, when it lies 24°

west of the Sun. Glowing at

magnitude 0.5, it easily out-

shines the background stars

of Aries the Ram.

Although Mercury lingers

for a few weeks, the best views

through a telescope come early

this month. At greatest elon-

gation, the planet shows an

8"-diameter disk that is slightly

more than one-third lit.

The Moon occults Mercury

June 3, but the only really good

location to view it from is South

Georgia Island in the South

Atlantic Ocean. From Husvik,

Mercury disappears behind the

waning crescent Moon’s bright

limb at 8h23m UT, though

the pair then stands only 2°

above the horizon. The planet’s

reappearance from behind the

Moon’s dark limb at 9h26m UT

will be a beautiful sight in

morning twilight.

The starry skyThe constellation Crux the

Cross rides high in the south

during June’s early evening

hours. The region just west of

there is strewn with wonderful

star clusters and nebulae worth

exploring through binoculars

and telescopes. The most

famous object in this area has

to be the Carina Nebula (NGC

3372), though I am also partial

to NGC 3532, a fine open clus-

ter not far away.

Roughly halfway between

Crux and these objects lies

another fine sight worth your

attention. The Pearl Cluster

(NGC 3766) resides in the

small section of southern

Centaurus that divides Crux

from Carina. To find it, scan 6°

west of magnitude 1.3 Alpha

(α) Crucis to pick up magni-

tude 3.1 Lambda (λ) Centauri,

then head 1.4° due north to the

beautiful cluster.

NGC 3766 shows up dimly

to the naked eye under a dark

sky, though it is easy to spot as

a small patch of light through

7x50 binoculars. The view

through a telescope shows two

pretty 7th-magnitude reddish

stars — one on each side of the

main group — among an oth-

erwise blue-white collection.

The Pearl Cluster made the

news in 2013 when astronomers

announced that they had dis-

covered a new type of variable

star within it. The stars exhib-

ited slight pulsations even

though they were of types that

don’t normally pulsate. The

idea became controversial in

2014, however, when a different

research team suggested that

these suns may be rapidly

rotating B-type stars of a type

that were already known as

pulsators.

STARDOME

OCTANS

CRUX CENTAURUS

NO

RM

A

LU

PU

S

LIB

RA

SER

PE

NS

CA

PU

T

SC

OR

PIU

S

CA

RINA

VE

LA

AN

TL

IA

PY

XI

S

HY

DR

A

CR

AT

ER

SE

XT

AN

S

CO

RV

US

PU

PP

IS

ARA E

LE

SCO

PIU

M

PAVO

APUS

TRIANGULUM

AUSTRALE

CIRCINUS

CHAMAELEON

HYDRUS

TUCANA

RETICULUM

DORADOPICTOR

VOLANS

MENSA

U R S A M A J O R

CA

NC

ER

CA

NIS

MA

JOR

LEO

L E O M

I NO

R

C O M AB E R E N I C E S

C A N E SV E NAT I C I

V I R G O

B O Ö T E S

C O R O NA

B O R E A L I S

LMC

SCP

SMC

NGC

2070

Denebola

Spica

Regulus

Alp

ha

rd

An

tare

s

Arcturus

M5

M51

NGP

M64

M104

M8

3

M66

M65

Canopus

M6

M4

Path of the Sun (ecliptic)

NGC 104

NG

C 6

231

NGC 5139

NGC 4755

NGC 3372

NGC

2516

NG

C2477

NGC

5128

NGC 6397

Sa

turn

Ma

rs

Jupiter

S

W

N

MAGNITUDES

Sirius

0.0

1.0

2.0

3.04.05.0

Open cluster

Globular cluster

Diffuse nebula

Planetary nebula

Galaxy

THE ALL-SKY MAP

SHOWS HOW THE

SKY LOOKS AT:

9 P.M. June 1

8 P.M. June 15

7 P.M. June 30

Planets are shown

at midmonth

OPHIUCHUS

SCUTUM

TEL

CORONA

AUSTRALIS

SAGITTARIUS

INDUS

HERCULESM

13

M11

M16

M17

M20

M22

M8

M6

M7

Saturn E

JUNE 2016

Calendar of events

1 The Moon passes 2° south of Uranus, 14h UT

3 Saturn is at opposition, 7h UT

The Moon passes 0.7° south of Mercury, 10h UT

The Moon is at perigee (361,140 kilometers from Earth), 10h55m UT

5 New Moon occurs at 3h00m UT

Mercury is at greatest western elongation (24°), 9h UT

6 Venus is in superior conjunction, 22h UT

11 Asteroid Flora is at opposition, 12h UT

The Moon passes 1.5° south of Jupiter, 20h UT

12 First Quarter Moon occurs at 8h10m UT

14 Neptune is stationary, 8h UT

15 The Moon is at apogee (405,024 kilometers from Earth), 12h00m UT

17 The Moon passes 7° north of Mars, 10h UT

18 Asteroid Pallas is stationary, 15h UT

19 The Moon passes 3° north of Saturn, 0h UT

Mercury passes 4° north of Aldebaran, 21h UT

20 Full Moon occurs at 11h02m UT

Winter solstice occurs at 22h34m UT

25 Asteroid Juno is stationary, 17h UT

26 The Moon passes 1.2° north of Neptune, 1h UT

27 Last Quarter Moon occurs at 18h19m UT

28 The Moon passes 3° south of Uranus, 23h UT

30 Mars is stationary, 8h UT

STAR COLORS:

Stars’ true colors

depend on surface

temperature. Hot

stars glow blue; slight-

ly cooler ones, white;

intermediate stars (like

the Sun), yellow; followed

by orange and, ulti mately, red.

Fainter stars can’t excite our eyes’

color receptors, and so appear white

without optical aid.

Illustrations by Astronomy: Roen Kelly

HOW TO USE THIS MAP: This map portrays

the sky as seen near 30° south latitude.

Located inside the border are the four

directions: north, south, east, and

west. To find stars, hold the map

overhead and orient it so a

direction label matches the

direction you’re facing.

The stars above the

map’s horizon now

match what’s

in the sky.

BEGINNERS: WATCH A VIDEO ABOUT HOW TO READ A STAR CHART AT www.Astronomy.com/starchart.

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