February 11, 2003Lynn Cominsky - Cosmology A3501 Professor Lynn Cominsky Department of Physics and...

February 11, 2003 Lynn Cominsky - Cosmology A350

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Professor Lynn Cominsky

Department of Physics and Astronomy

Offices: Darwin 329A and NASA EPO

(707) 664-2655

Best way to reach me: [email protected]

Astronomy 350Cosmology


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GEMS: Invisible Light Sources

and Detectors

Different stations have different types of light sources and detectors

All stations have same set of materials Try each of the 5 stations For each material: Predict whether or not it will

block the light, then test your prediction Write your predictions and results down on the

worksheets that are provided Hand in worksheets before leaving class


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SIRTF video

Seeing the World with Infrared EyesStarring Michelle Thaller from JPLInfrared is brighter where things are

hotter

Also –check out this powers of ten java applet on line - http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/


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Looking back through space and time

Constellation-X

JWST, FIRST

MAP, Planck

LISA, GLAST

Big Bang inflation

first stars, galaxies,

and black holes

clusters and groups of galaxies

microwavebackground

matter/radiationdecouplingEarly Universe Gap

First Stars Gap


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Ultimate Time Machine

Doing astronomical observations is like traveling back in time

If an galaxy is 1 million light years away, then the light that you are seeing left that galaxy 1 million years ago, and you are seeing what it looked like long ago

Do the Time Machine Activity


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Powers of Ten

Earthdiameter

~1.3 x 104 km


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Powers of TenSolar System

diameter ~5.9 x 109 km


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Solar System

Relative sizes and order of planets

Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto


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Planet Distance Orbital Period Diameter Mass Moons

(103 km) (days) ( km) (kg)

Mercury 57910 87.97 4,880 3.30e23 0

Venus 108200 224.70 12,104 4.869e24 0

Earth 149600 365.26 12,756 5.9736e24 1

Mars 227940 686.98 6,794 6.4219e23 2

Jupiter 778330 4332.71 142,984 1.900e27 39

Saturn 1429400 10759.50 120,536 5.68e26 30

Uranus 2870990 30685.00 51,118 8.683e25 21

Neptune 4504300 60190.00 49,532 1.0247e26 8

Pluto 5913520 90800 2274 1.27e22 1

Solar System


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Formation of the Solar System Activity

Examine the figures and tables that are provided in the handout

Answer the questions on the worksheetFeel free to discuss them with your

neighbor!


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Solar system architecture

The planets are isolated from each other without bunching, and they are placed at orderly intervals

The planets' orbits are nearly circular, except for those of Mercury and Pluto.

Their orbits are nearly in the same plane; Mercury and Pluto are again exceptions.

All the planets and asteroids revolve around the Sun in the same direction that the Sun rotates (from west to east).


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Except for Venus, Uranus, and Pluto, the planets also rotate around their axes from west to east.

Studies of chemical composition suggest that the small, dense Terrestrial planets are rocky bodies that are poor in hydrogen; the large, low-density Jovian planets are fluidlike bodies that are rich in hydrogen; and most of the outer planets' satellites, comets, and Pluto are icy bodies.


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The Terrestrial planets have high mean densities and relatively thin or no atmospheres, rotate slowly, and possess few or no satellites--points that are undoubtedly related to their smallness and closeness to the Sun.

The giant planets have low mean densities, relatively thick atmospheres, and many satellites, and they rotate rapidly--all related to their great mass and distance from the Sun.


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Formation of the solar system

Animation shows a simplified model


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Solar system formation

Protoplanetary Nebula hypothesis: Fragment of interstellar cloud separates Central region of this fragment collapses to form

solar nebula, with thin disk of solids and thicker disk of gas surrounding it

Disk of gas rotates and fragments around dust nuclei– each fragment spins faster as it collapses (to conserve angular momentum)

Accretion and collisions build up the mass of the fragments into planetesimals

Planetesimals coalesce to form larger bodies


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Solar System Formation

Formation of the SunSolar nebula central bulge collapsed to

form protosunContraction raised core temperatureWhen temperature reaches 106 K, nuclear

burning can startSolar winds could have blown away

remaining nearby gas and dust, clearing out the inner solar system


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Formation of Inner Planets

While the terrestrial planets formed (and shortly thereafter), they were bombarded by many planetesimals

Bombardment made craters and produced heat which melted the surfaces, releasing gases to form atmospheres, and forming layered structures (core, mantle, crust)

Additional heat provided by gravitational contraction and radioactivity


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Cratering

Mercury and the Moon show the results of bombardment during early formation of solar system

Mercury

Moon


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Earth’s Surface

Q: Why does the Earth’s surface show little evidence of cratering?

Bombardment of Earth was similar to that of the Moon, Venus, Mars and Mercury

A: Earth’s surface is actively reforming due to volcanic activity, erosion from water, plate tectonics,etc.


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Volcanic Activity

Io Jupiter’s Moon) shows volcanic activity

Venus also has lava flows Prometheus volcano on Io

Magellan Radar image of Venus


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Erosion and Water

Erosion (most likely due to liquid water) also seems to have affected Mars, which also has mountains and craters

Moon has frozen water at poles but no signs of erosion

Mars


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Where is the Water?

Europa (Jupiter’s Moon) thin outer layer of water ice (1-10

km thick) possible liquid water ocean

underneath the surface

Callisto (Jupiter’s Moon)• Ice-rock mix throughout

• Possible salt water underneath surface


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Where is the Water?

Saturn Rings are mostly water ice Will be studied by Cassini

in 2004

Titan (Saturn’s Moon) Water icebergs in an ocean

of methane? No water in atmosphere Huygens probe will be

dropped from Cassini


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Elements in the Planets

Chemical composition at formation depended on temperature (mostly determined by distance from Sun)

Asteroid belt had lower temperature, so carbon and water-rich minerals could coalesce in the planetesimals

From Jupiter outwards, temperatures were much lower, so frozen water coalesced with frozen rocky material, or at even lower temperatures, frozen methane or ammonia


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Formation of Moon

Lunar samples from Apollo revealed the similarity (but some differences) between the materials in the Earth’s crust and mantle and the Moon

Collisional ejection would explain these similarities – a Mars sized body impacts the cooling Earth – part is absorbed, part splashes out material which cools to form the Moon

Problems remain with the lunar orbital plane vs. the equatorial plane of the Earth


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Formation of Earth’s Moon

Simulation shows formation of Moon due to impact on Earth


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Formation of Outer Planets

In the outer, cooler regions, icy planetesimals collided and adhered.

Hydrogen and helium were then accreted onto these Earth-sized bodies.

More H and He adhere to larger bodies, explaining their relative lack in Uranus and Neptune

Uranus and Neptune are richer in heavier elements such as C, N, O, Si & Fe


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Formation of Outer Planets

Formation of moons of Jupiter and Saturn are mini-versions of the solar system evolution

Heat from Jupiter when it formed resulted in inner moons that are rocky, and outer moons that are icy

Comets and Kuiper belt objects are remnants of original icy planetesimals, located far from Sun


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Rings

Saturn has 7 named rings (A-F)

Jupiter has faint dark rings

A-ring

B-ring

Cassini divisionEncke

division


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Rings

Uranus has 11 known rings

HST image of Uranus and its rings

Neptune has 3 dark rings

HST image of Neptune


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Formation of Rings

Rings appear too young to be primordial – maybe only 108 y - i.e., they must have formed after the planets

Rings are ubiquitous in the outer planets – whereas we once thought they were rare (only Saturn had rings)

Perhaps collisions between moons and interlopers provides material for the rings – seems to work for Uranus and Neptune, but not for Jupiter and Saturn


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Formation of Rings

Saturn’s rings have a resonant relationship with its satellites – i.e., the satellites sweep out gaps between the rings and create fine structure in the patterns seen in the rings

A-ring Resonance – the satellite Janus orbits Saturn 6 times while the ring material orbits 7 times, creating a six-lobed structure at the ring’s outer edge

Cassini gap – Mimas has a 2:1 resonance with the outer edge of the B-ring at the gap


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Is Pluto really a planet?

Smallest planet, has elliptical, highly inclined orbit

Usually furthest from Sun, but orbit crosses inside Neptune

Smaller than 7 moons in our solar system But it has its own moon named Charon It resembles asteroids Rock and ice, little atmosphere

Pluto and Charon


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Meteorites

Most meteorites are chunks of asteroids, the Moon or Mars; some are from comets

>50 billion meteorites have traveled between Earth and Mars since the birth of the solar system

Panspermia = Life comes from space Some think meteorites could have carried

life from Mars to Earth or vice versa


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Life on Mars?

“Face on Mars”

1976 Viking ViewMars Global Surveyor Image April 2001


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Life on Mars? Martian Meteorite Found in Antarctica in 1984 but origin is Mars Left Mars 16 million years ago, arrived in Antarctica

13,000 years ago Evidence of water infiltration while on Mars Carbonite mineral globules contain shapes that could be

dead, fossilized bacteria and their byproducts

Meteorite Carbonate Globules

Fossilized Shapes


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Planetary Missions

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging), being built for launch in 2004, arrives at Mercury in 2009

Venus program – no current plans Mars program - Pathfinder (1996), Global

Surveyor (1999) then two disasters. Two new Rover missions are in the works – with launches in May 30 and June 25, 2003

Landings on Mars - January 4 & 25, 2004


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Planetary Missions

Galileo mission is orbiting Jupiter, currently sending back data – flew by Io on 1/17/02, and by Amalthea on 11/05/02 --will plunge into Jovian atmosphere in September 2003

Tape recorder failures incurred when Galileo flew close to Jupiter in November during the Amalthea flyby. Data are just now being recovered. Amalthea data may be present on the tape recorder, have not yet been released.


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Cassini mission to Saturn arrives July 2004. Will drop an ESA probe (Huygens) onto Titan, and flyby Titan and three smaller moons.

New Horizons - Pluto –Kuiper belt mission was chosen, and funded through 2002 by NASA. FY03 budget is uncertain. If funded, will launch in 2006, arrive at Pluto by 2015

Europa orbiter still on hold, not in FY03 budget. New propulsion technology is being developed to speed up the journey.

Planetary Missions


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Planets around other stars

Over 100 planets around other stars are known


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PSR 1257+12 (a radio pulsar, Wolczan 1995)3 objects orbiting this stellar corpse

1 is the size of the Moon

2 are the size of the Earth

probably formed after the supernova explosion that made the pulsar

51 Pegasi (Sun-like star, Mayor and Queloz 1996) at least one object, about 1/2 of Jupiter

orbit of only 4 days

closer to star than Mercury, so very hot

42 light years from Earth


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70 Virginis (Sun-like star, Marcy and Butler 1996) 116 day orbit

9 Jupiter masses (1 Jupiter = 317 Earth masses)

temperature of planet may allow liquid water to exist


47 Ursae Majoris (Marcy and Butler 1996) 1100 day orbit

3 Jupiter masses

temperature of planet may allow liquid water to exist



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Another solar system

Upsilon Andromedae: Multiple planet solar system discovered by Marcy et al.

a) 4.6 d

b) 240 d

c) 1313 d

Ups And


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How they find extra-solar planets

Stars are too bright to see reflected light from planets directly

Unseen planet causes star to wobble as it orbits – star’s light is Doppler shifted


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Doppler Shift

Wavelength is shorter when approaching

Stationary waves

Wavelength is longer when receding


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Doppler Shift

Comparison of laboratory to blue-shifted object

Comparison of laboratory to red-shifted object


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Doppler Shift

Doppler shift song by AstroCapella


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Other methods:

Astrometry – measuring the exact position of a star as it wobbles

Hipparcos was an ESA satellite operational from 1989-93


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Other methods:

Photometry – measuring the change in brightness of a star as a planet transits in front of it, obscuring some of the light (~2%)


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The first transiting planet

HD209548 – a visualization by Aurore Simonnet


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The first transiting planet

STARE project found the first transit in HD209548 – Brown and Charbonneau 1999

The planet’s mass is 63% of Jupiter (about 200 Earth masses) with radius 1.3 times Jupiter density 0.39 g/cm3 (< water!)

It transits the star every 3.5 days Its atmosphere is very hot (1100oC) since it is only 6.4

million km from the star When the planet passed in front of the star, the star’s

light passed through the planet’s atmosphere and sodium was observed by HST


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Saturn mass planets (95 times Earth)

Both planets are very close to their stars - This makes them easier to detect

If each planet orbited the Earth’s Sun:


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Latest news (1/6/03)

Transiting observation used to discover planet in constellation Sagittarius OGLE TR-56b

Most distant and hottest planet yet found – 29 hour “year” for Jupiter-sized planet

Transiting planets can be seen to smaller sizes than Doppler Shift technique, offering the possibility that Earth-sized planets can someday be spotted

Millions of candidates events were analyzed in the OGLE survey (was looking for gravitationally lensed events) to find 59 possible transiting planets. These were studied using a bigger telescope, and – this one is confirmed, and 2 more may be.


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Formation of other solar systems

Most extra-solar planets that have been discovered have “hot Jupiters” – very close to star compared to our system

Most are also found in elliptical orbits vs. circular orbits in our solar system

It is hard to explain elliptical orbits in solar systems of any age.

Close orbits can be explained by the initial formation of the planet further away, then a migration in towards the star.


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Disks around stars

There is much evidence of disks with gaps (presumably caused by planets) around bright, nearby stars, such as Beta Pic


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Jupiter’s role in evolution of life

Jupiter is believed to have a role in keeping the Earth (relatively) free from bombardment that could end life

Nevertheless, there have been at least 6 mass extinctions on the Earth – one bombardment is believed to have killed the dinosaurs – and that wasn’t even the worst one!

A theory has been advanced that our quasi-periodic mass extinctions are due to the passage of another planet on a very elliptical orbit “Nemesis”

No evidence (other than fossil records) supports the Nemesis theory


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Mass extinctions

Mass extinctions occur every 26-30 million years

This one killed the dinosaursThis one

killed 95% of all life


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Solar System habitability factors

• Temperature range (–15o C to +115o C on Earth)

• Protection (look what happened to the dinosaurs!)

• Light (or other source of heat or energy)

• Liquid water (geothermal or atmospheric cycles)

• Nutrients (chemicals, vitamins, minerals, fertilizers)

• Energy source (light, food, carbohydrates, fats, sugars)


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What makes a world habitable?

In groups of 3-4, take a set of cards that summarize the properties of various solar system bodies Temperature Water Atmosphere Energy Nutrients

Consider the following: What does life need? What kinds of conditions might limit life?

Select your top three candidates for life


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Web Resources

Nine Planets tour http://www.seds.org/nineplanets/nineplanets

Mercury MESSENGER mission: http://sd-www.jhuapl.edu/MESSENGER/Mars Exploration program

http://mpfwww.jpl.nasa.gov/Galileo mission

http://galileo.jpl.nasa.gov/


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Web Resources

New Horizons Pluto mission http://pluto.jhuapl.edu/mission.htm

Europa orbiter http://www.jpl.nasa.gov/europaorbiter/EO_Info.htm

Transiting planet OGLE-TR-56b http://cfa-www.harvard.edu/press/pr0301.html

Mass extinctions http://www.bbc.co.uk/education/darwin/exfiles/quest1.htm

Solar System Formation activity http://www.astro.washington.edu/labs/clearinghouse/labs/Formss/lab.html


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Web Resources

Extra-solar planet searcheshttp://exoplanets.org

STARE: http://www.hao.ucar.edu/public/research/stare/stare.html

Solar System architecture http://www.physics.gmu.edu/classinfo/astr103/CourseNotes/ECText/ch11_txt.htm#11.1.

Hipparcos Space Astrometry Mission http://astro.estec.esa.nl/Hipparcos/

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February 11, 2003Lynn Cominsky - Cosmology A3501 Professor Lynn Cominsky Department of Physics and...

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