Our Place in Space

Our Place in Space Earth: (small) 15 thousand km

(12,000 miles) in diameter Sun: 15 million km in diameter Solar System: about 6 billion km in

diameter

Our Place in Space Milky Way Galaxy - 1000 quadrillion

km or 100,000 light years in diameter

It would take a beam of light 100,000 years to cross the entire galaxy!

The Milky Way Galaxy

Hubble Space Telescope (HST) Deep-Field Camera Photo – Every Dot or “Smudge” is a

Galaxy!

Constellations Patterns of stars in the night sky Named after mythological beings,

heroes or animals 88 constellations (mostly Greek) are

recognized in the Western world Different cultures grouped stars

differently

Constellations Ecliptic – plane in which the Sun &

planets travel Zodiac – 12 major constellations in

the ecliptic

Constellations Astrology (not a science)

uses relative positions of stars and planets to attempt to predict the future

Astronomy & astrology were once the same in the distant past

Polaris is Part of a Triple-Star System – Artist Concept

Stars

They are other Suns

Many different type

• Stellar classification– Most stars are currently classified using the

letters O, B, A, F, G, K, and M, where O stars are the hottest and the letter sequence indicates successively cooler stars up to the coolest M class.

– Quick quiz• Arrange in order from hottest to coolest

– A, B, F, G, K– O, M, A– B, A, K,O, M

Here they are

Are stars on fire?!

• Dr. Feynman– Oooooook, so are stars on fire Mr. McCormick?

• Not exactly.– Stars turn mass into energy. They really don’t burn

anything.• Stars turn mass into energy

– E = mc2

They do this!

All stars do this

• Every star, no matter how large or small, no matter where they are; every star starts its life with the proton-proton chain

• Failed stars and so called dark objects, objects that might have become stars if given enough mass, never start the p-p chain.

• Lets make sure we understand this fully.– Take out a piece of paper and draw, IN GOOD

DETAIL, the p-p chain

Buzz words

• Stars produce light, we can see them.– Go out tonight and look up at the stars, they are

very beautiful.• About 99% of our solar system’s mass is tied up

in the star. – Planets, comets, gas giants, etc…

• So when we look at a galaxy we only see stars and they make up about 99% of the solar system they create.

Buzz words cont

• So only about 1% of a galaxy should be “dark matter”, stuff that doesn’t make light

• Comets, planets, asteroids, and gas giants.

• However, most of the mass in a galaxy is made up of dark matter………so you know…..that's a problem.

Bayer designation

• A Bayer designation is a stellar designation in which a specific star is identified by aGreek letter, followed by the genitive form of its parent constellation's Latin name

example

BayerDesignation

ApparentMagnitude

ProperName

α Ori 0.45 Betelgeuse

β Ori 0.18 Rigel

γ Ori 1.64 Bellatrix

δ Ori 2.23 Mintaka

ε Ori 1.69 Alnilam

ζ Ori 1.70 Alnitak

• We will learn these symbols.– I think its neat– It’s a dying language– It’s the language of the

discipline of science we are coving

– I think its neat

Astronomy

Two words, two ideas

• Astronomy – The study of the stars.– Size– Temperature– Life cycle– Movement– Content– etc

• Cosmology – the study of the universe– Content

• Time frame– Size– Speed– Open, closed, expanding– etc

What do stars produce?• Radiation - radio waves

– 10^3 – 10^9• Microwaves*

– 10^10 – 10^11• Infrared

– 10^12 – 10^14• Visible light

– ~10^14-10^15• Ultraviolet

– 10^15 – 10^17• X ray

– 10^17 – 10^19• Gamma

– 10^20 – 10^23

• Particles – Before death

• He to Fe– At death

• Fe to Cn

– Before and during• Neutrinos• Cosmic rays

– Beta and alpha particles• Pretty much the entire particle zoo

– Death• Depends on the state.

How to capture Radiation • CCD (Charge Couple Device)

– cannot store digitally– Optical telescopes

• Pages 44-46 chapter 2– Infrared– Ultraviolet– X ray– Gamma ray

• Before CCD you used glass plates with sliver nitrate and exposed to light.

• Radio telescopes– Page 47

• Store signals digitally– Computer

• Many types of software do this.• Mainly found in commercial

radio stations.

• **side note– Super easy to create a large

array of radio dishes to collect tons of data.• HOWEVER, not the “good” type

of data.

Early missions

• Rockets - Two types– Liquid vs solid• Read and know the difference

• Best way to get out of the earth’s atmosphere• Satellites started space race

So lets act like baby astronomers

• Wien’s Displacement Law– λmax T = .290 cm K• Where λmax is the maximum wavelength produced by

the star• T is the temperature of the star

• Primarily used by photometry related astronomers.

There is a relationship between wavelength and temperature

Example problems

• We observe a star with surface temperature of ~ 3400 K. – What is its peak wavelength?– What type of star is it?

• We observe a star with peak wavelength of 4.53 X 10^-4 cm– What type of wavelength of light does it produce?– How hot is the star?

wavelengths

• Transverse – How light travels

• Wave travels 90degrees perpendicular to direction of displacement

• Longitudinal– How sound travels

• Wave travels in the SAME direction of displacement

Longitudinal

Transverse

Wave, particle, why not both?

• Light acts as both a wave and a particle• Particles with low mass also act as both a

wave and a particle• The more mass, the less wave-like qualities an

object has.• DeBroglie Wavelength

Exo planets

• Extra solar planets– Exo planets for short– Planets outside our solar system– 25 direct images• Pictures

– 707 photometry or radio velocities– Some 3600 Kepler candidates– . Over 4000 total

Photometry detection

Real data!!

How cool is this?!

KNOW THIS PROBLEM FOR THE TEST

• Some star with radius, r = 12, has a planet that orbits it ever 3 days. If you happen to observe this star for 12 days you will see a transit event. Your CCD detects 100 photons BEFORE the transit and only 80 photons DURING transit. – What percentage of the star is covered by the

planet?– 8th grade only: what is the radius of the planet?

solution• 1st – find the percentage difference in the amount of

photons, BEFORE – DURING.– 100 -80 = 20

• So 20% or .20 of the photons are lost due to transit

• 2nd – using the surface area formula solve for the surface area of the star.– 3.14 X 12 X 12 (or 12^2) = 452

• 3rd – multiply area of star by % lost to get the area of the planet.– 452 X .20 = 90

• 8th grade cont to next slide

8th grade cont

• Having solved the area of the planet, 90, plug that back into the area formula, this time solving for r. r = square root (area/3.14)– Your answer should be 5.3