GEARS Workshop Tuesday

GEARS Workshop Tuesday

2012

Warm Up• Good morning!• Complete form online • Complete paper evaluation up to activities

completed – if available already• Create a code name to add to top of sheet so

you can get the same one back each day – OR keep yours safe all week to turn in on Friday.

Flux Simulator• Flux Simulator for Fluxiness we found

So for same bulb – 2 different distances – get 2 fluxes

Engage: Flux Lab• How can we use the inverse square law of

light to find out how luminous the sun is?• Think for a few minutes in groups.

Brainstorming.

Flux Lab – groups of 3-4• Demonstrate the concept in the room with 2

light bulbs.• Explain that there are 2 measurements to

make – distance to bulb for equal brightness wax – each

person decides – Color of wax on each side when equal brightness

Photometer Lab Equation

22

22

1

1

)()( dist

L

dist

L

One of these items is the light bulbOne of these items is the SunL is the powerNot the same ‘bulb’ as in prior slide

Discussion• % error • Color – each person better have something

written down• Sources of error: Brainstorm

% error• Used when know actual value and you are

doing a verification lab. • Provides a measure of the accuracy of your

results (hint – see characteristics of science)

% difference• Used when you don’t know the answer.

Provides a measure of the precision of your results.

• Helps identify outliers.

Accuracy & Precision

Wien’s Law – Color and Temperature

Wavelength in meters from this formula1 nanometer = 10-9 meter1 meter = 109 nanometer

Find Temperature of the Sun• You need the radius of sun from the pinhole camera

experiment. (Surface Area of a sphere… is)• Use Stefan-Boltzmann (hyper-physics calculator for

power/area - http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html)

• Or Wolfram Alpha calculator (http://www.wolframalpha.com/entities/calculators/stefan-boltzmann_law/mn/o0/q0/)

• Prize to the group with the closest measurement if your workshop facilitator thinks it is OK

Find color of the Sun• http://science-edu.larc.nasa.gov/EDDOCS/

Wavelengths_for_Colors.html• Compare with what you saw.

Explain: Flux Lab• We used inverse square law model & known source• We assumed Sun was blackbody (known from other

observations) • We used Stefan-Boltzmann model and pinhole

camera radius (from geometry and knowing distance) to get temperature of the sun as blackbody

• We used Wien’s Law model for peak wavelength of blackbody emitter using the temperature

Models• Models (aka theories, math equations,

previously tested ideas) help extend our knowledge of the world around us

• Why can’t we just go measure the temperature of the Sun?

• How do we measure anything in astronomy?

Sun• Sun & Space Weather – if have DVDs available.• Jhelioviewer• Teaching EM Spectrum with the Sun – lesson

plan presented at NSTA by Webster & Aguilar•

Elaborate: Intrinsic Properties of Stars

• Let’s think back to initial categories made of star image

• Having made a few measurements now – let’s list the intrinsic properties of stars on the board together

Organizing Stars• Astronomers want nothing more than to

classify and categorize – just like every other scientist

• First thing we do is try to plot things on graphs to see if there is a pattern

• Let’s plot two intrinsic properties against one another.

This is on board – not in powerpoint

• Start with axes only• Point out logarithmic scaling• Point out backwards temperature• Add main sequence – units of solar lum – what

that mean• Test for understanding – ask where blue stars• Ask where red stars• Ask where luminous, cold, hot, less luminous

• Add white dwarfs• Ask for understanding – hot cold dim not• Add supergiants• Add giants

• Hey.. You know – dwarfs, giants.. Seems to imply something about radius

• Blackbodies follow Stefan-Boltzmann relation• Luminosity and temperature and radius all

related.

Radius on HR diagram

WOW!• What a great diagram – 3 intrinsic properties

in one graph!

Mass?• Yes indeedy… mass for main sequence is on

this diagram too. • Luminosity – Mass Relation

Age on diagram?• Sort of – if high mass main sequence star –

know something. As they fuse such a short time

• If a high mass star is “on” main sequence – know it is young!

• But what about if it is a G star, like the Sun? Is it 2 billion years old? 1 billion?

• Need groups of stars and use a model

Composition?• No… but hey• Luminosity, Mass, temperature, radius, and

age… on one graph!• Models of blackbodies allow us to know more

about stars than we can get from observations alone.

Elaborate more: Create a diagram

• If time – if not, assign for HW. (11:30 data files – some are on usb key)

• Nearby Stars• Bright Stars• Cluster 1• Put all on same axes!

Your Graphs• Did all the graphs look the same?

Misconceptions about HR• Motion – actually a time evolution – for a

single star – temperature

Stellar Evolution• Engage: What are some questions you have

about stars right now?• Brainstorm a list on your whiteboards.

Explore: Stellar Evolution• Simulators – as on agenda. • Is the main sequence for stars on the L-T

diagram a sequence of age?

Explain• Stars are simply balance (or imbalance) of forces – in

vs. out. • Formation – gravity stronger than gas pressure force• Main sequence – gravity in balance with gas pressure

force (btw – fusion!)• Unbalance signals end of main sequence –exciting

things happen• Then back in balance for end state

Explain: • Do all stars evolve the same way?• Do all stars take the same amount of time to

evolve?• What is your evidence to support your claim?• (from the simulators…)

Outcomes – from AstroGPS• Identify end phases of stars like the sun• Match evolutionary stages to initial mass

ranges• Relate atmospheric properties to astronomical

equipment needed• Relate mass of star to lifetime and power • Correctly identify colors and luminosities of

stars using an HR diagram

NASA’s Great Observatories• http://coolcosmos.ipac.caltech.edu/cosmic_classroom/

cosmic_reference/greatobs.html • http://www.nasa.gov/audience/forstudents/postsecondary/

features/F_NASA_Great_Observatories_PS.html • Today we are going to look at some of the data from Chandra. • The next 2 images are examples of what you can do with

observations at multiple wavelengths of same part of sky

Summary: • Really high mass• High mass• The Sun and the lower mass stars• http://cheller.phy.georgiasouthern.edu/

gears/Units/2-StellarEvolution/2Stars_7.html • Compare main sequence lifetimes, end states.

End of Stars• Main sequence is the stage of existence where

stars are fusing hydrogen to helium• Spend largest fraction of their existence doing

this• More massive stars – short lived• Low mass stars – long lived• Range – 100,000 years – 100 billion years!

Red Giant• BP Psc is a star like our Sun, but one that is more evolved, about 1,000 light years away.• New evidence from Chandra supports the case that BP Psc is not a very young star as

previously thought.• Rather, BP has spent its nuclear fuel and expanded into its "red giant" phase – likely

consuming a star or planet in the process.• Studying this type of stellar "cannibalism" may help astronomers better understand how stars

and planets interact as they age.•

The composite image on the left shows X-ray and optical data for BP Piscium (BP Psc), a more evolved version of our Sun about 1,000 light years from Earth. Chandra X-ray Observatory data are colored in purple, and optical data from the 3-meter Shane telescope at Lick Observatory are shown in orange, green and blue. BP Psc is surrounded by a dusty and gaseous disk and has a pair of jets several light years long blasting out of the system. A close-up view is shown by the artist's impression on the right. For clarity a narrow jet is shown, but the actual jet is probably much wider, extending across the inner regions of the disk. Because of the dusty disk, the star's surface is obscured in optical and near-infrared light. Therefore, the Chandra observation is the first detection of this star in any wavelength.

BPPSC – Red Giant – on left. Artist conception - right

Planetary Nebula

White Dwarf• An international team of astronomers, studying the left-over remnants of stars like

our own Sun, have found a remarkable object where the nuclear reactor that once powered it has only just shut down. This star, the hottest known white dwarf, H1504+65, seems to have been stripped of its entire outer regions during its death throes leaving behind the core that formed its power plant.

• The Chandra X-ray data also reveal the signatures of neon, an expected by-product of helium fusion. However, a big surprise was the presence of magnesium in similar quantities. This result may provide a key to the unique composition of H1504+65 and validate theoretical predictions that, if massive enough, some stars can extend their lives by tapping yet another energy source: the fusion of carbon into magnesium. However, as magnesium can also be produced by helium fusion, proof of the theory is not yet ironclad. The final link in the puzzle would be the detection of sodium, which will require data from yet another observatory: the Hubble Space Telescope. The team has already been awarded time on the Hubble Space Telescope to search for sodium in H1504+65 next year, and will, hopefully, discover the final answer as to the origin of this unique star.

White dwarf – Artist impression

Supergiant to Supernova

Star Death• A composite image from NASA's Chandra (blue) and Spitzer (green and

red-yellow) space telescopes shows the dusty remains of a collapsed star, a supernova remnant called G54.1+0.3. The white source at the center is a dead star called a pulsar, generating a wind of high-energy particles seen by Chandra in blue. The wind expands into the surrounding environment. The infrared shell that surrounds the pulsar wind, seen in red, is made up of gas and dust that condensed out of debris from the supernova explosion. A nearby cluster of stars is being engulfed by the dust.

• The nature and quantity of dust produced in supernova explosions is a long-standing mystery, and G54.1+0.3 supplies an important piece to the puzzle.

G54.1+0.3 Pulsar with wind

Crab SNR + Pulsar

Black Holes• http://hubblesite.org/explore_astronomy/

black_holes/

Black Hole• G1915

+105. 14 solar masses.

Fe In BH• Using Chandra spectra obtained from more

than 300 supermassive black holes in the centers of galaxies, a team of astronomers has been able to determine the amount of iron near the black holes (light blue in illustration on the right). The black holes were all located in the North and South Chandra Deep Fields, where the faintest and most-distant X-ray objects can be identified.

Stars• We’ve spent some time looking at properties

of blackbodies and learning how to learn about astronomical objects that we can’t get close to

• Temperature and color• Temperature and overall luminosity• Inverse square law of flux -> observed

brightness

Evaluate: Can you fill in this concept map?

• Vocab – Red Giant, black hole, white dwarf, planetary nebula, neutron star, supernova

Star Formation• What are some of the things you notice about

places where we find young stars?• Look at the images – note common features

Star Formation

M16 – X-ray stars

What did you observe?

Star Formation• Accompanied by dust!– Collapse requires cold – think ideal gas law– “Dust” protects from light from nearby stars that

might heat gas

• Wispy gas – the future fuel for the star• And some very powerful stars that are very

high temperature – emitting lots of light at X-ray and UV- the signatures of young stars

Patterns + models = stellar evolution theory

• Along with physical models of gravity, gas pressure, electrostatic repulsion, nuclear physics

• Plus some nice spectral line measurements• Get a beautiful scenario of stellar evolution• Imagine the Universe powerpoint

Pretty Picture Finder• http://www.nasaimages.org/

http://heritage.stsci.edu/http://www.spitzer.caltech.edu

HR diagram & Stellar Evolution

• Review where main sequence stars, super giants, and white dwarfs are on HR diagram

Star Lifetimes• http://astrosun2.astro.cornell.edu/

~mcomins/lab10_solutions.pdf

Cluster ages• What is a cluster? And why are they

important?• Globular cluster distribution told us shape of

our own galaxy• Globular clusters helped us learn about

interstellar “dust”• Help us determine age of our galaxy

M30 Cluster

Clusters of stars – ages

Which one is younger?

Go back to diagrams made earlier in XL

• What can those clusters tell you now about age of the cluster? At least relative ages?

Extra fun question• High mass stars fusion Hydrogen to Helium• So do low mass stars• Stars are made up primarily of Hydrogen• So… high mass stars should have lots more

hydrogen to fuse than low mass stars• How come high mass stars fuse hydrogen for

so much less time?

Misconception alert• http://aspire.cosmic-ray.org/labs/star_life/

hr_interactive.html• Comes from images like on next page.

Life after main

sequence

Journey to the Stars • Pairs: One watch and jot down areas in which

students could have misconceptions or in which a misconception is addressed

• One watch and note some ‘student worksheet’ ideas.

Extra bonus material• It seems like temperature measuring is hard –

have to figure out the exact place of the peak wavelength or know the radius of star

• So is luminosity measuring – adding up all the light at all wavelengths…

• How do we really measure temperature and luminosity?

• Magnitude (absolute in a filter, such as U, B, V, R, I, J, K)

• and ‘color’ which is difference between two magnitudes (e.g. B-V, U-B, J-K)

• http://astro.unl.edu/naap/blackbody/blackbody.html• http://astro.unl.edu/naap/blackbody/filters.html • http://astro.unl.edu/naap/blackbody/animations/

filters.html

Outcomes• Identify end phases of stars like the sun• Match evolutionary stages to initial mass

ranges• Relate atmospheric properties to astronomical

equipment needed• Relate mass of star to lifetime and power • Correctly identify colors and luminosities of

stars using an HR diagram