Astronomy 350 Cosmology

1. Astronomy 350Cosmology Professor Lynn Cominsky Department of Physics and Astronomy Offices: Darwin 329A and NASA EPO (707) 664-2655 Best way to reach me: lynnc@charmian.sonoma.edu Lynn Cominsky - Cosmology A350

2. 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 Lynn Cominsky - Cosmology A350

3. Looking back through space and time Constellation-X JWST, FIRST MAP, Planck clusters and groups of galaxies LISA, GLAST first stars, galaxies, and black holes matter/radiation decoupling microwave background Big Bang inflation Early Universe Gap First Stars Gap Lynn Cominsky - Cosmology A350

4. Ultimate Time Machine • Doing astronomical observations is like travelling 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 Lynn Cominsky - Cosmology A350

5. Powers of Ten Earth diameter ~1.3 x 104 km Lynn Cominsky - Cosmology A350

6. Powers of Ten Solar System diameter ~5.9 x 109 km Lynn Cominsky - Cosmology A350

7. Solar System Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Relative sizes and order of planets Lynn Cominsky - Cosmology A350

8. Solar System 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 Lynn Cominsky - Cosmology A350

9. Formation of the Solar System Activity • Examine the figures and tables that are provided in the handout • Answer the questions on the worksheet • Feel free to discuss them with your neighbor! Lynn Cominsky - Cosmology A350

10. 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). Lynn Cominsky - Cosmology A350

11. Solar system architecture • 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. Lynn Cominsky - Cosmology A350

12. Solar system architecture • 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. Lynn Cominsky - Cosmology A350

13. Formation of the solar system Animation shows a simplified model Lynn Cominsky - Cosmology A350

14. 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 Lynn Cominsky - Cosmology A350

15. Solar System Formation • Formation of the Sun • Solar nebula central bulge collapsed to form protosun • Contraction raised core temperature • When temperature reaches 106 K, nuclear burning can start • Solar winds could have blown away remaining nearby gas and dust, clearing out the inner solar system Lynn Cominsky - Cosmology A350

16. 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 Lynn Cominsky - Cosmology A350

17. Cratering Moon Mercury • Mercury and the Moon show the results of bombardment during early formation of solar system Lynn Cominsky - Cosmology A350

18. 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. Lynn Cominsky - Cosmology A350

19. Volcanic Activity Prometheus volcano on Io • Io Jupiter’s Moon) shows volcanic activity • Venus also has lava flows Magellan Radar image of Venus Lynn Cominsky - Cosmology A350

20. 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 Lynn Cominsky - Cosmology A350

21. 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 Lynn Cominsky - Cosmology A350

22. 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 Lynn Cominsky - Cosmology A350

23. 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 Lynn Cominsky - Cosmology A350

24. 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 Lynn Cominsky - Cosmology A350

25. Formation of Earth’s Moon Simulation shows formation of Moon due to impact on Earth Lynn Cominsky - Cosmology A350

26. 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 Lynn Cominsky - Cosmology A350

27. 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 Lynn Cominsky - Cosmology A350

28. Rings A-ring B-ring Encke division Cassini division • Saturn has 7 named rings (A-F) • Jupiter has faint dark rings Lynn Cominsky - Cosmology A350

29. Rings HST image of Uranus and its rings HST image of Neptune • Uranus has 11 known rings • Neptune has 3 dark rings Lynn Cominsky - Cosmology A350

30. 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 Lynn Cominsky - Cosmology A350

31. 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 Lynn Cominsky - Cosmology A350

32. 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 Lynn Cominsky - Cosmology A350

33. 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 Lynn Cominsky - Cosmology A350

34. Life on Mars? • “Face on Mars” Mars Global Surveyor Image April 2001 1976 Viking View Lynn Cominsky - Cosmology A350

35. 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 Lynn Cominsky - Cosmology A350

36. 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 Lynn Cominsky - Cosmology A350

37. 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. Lynn Cominsky - Cosmology A350

38. Planetary Missions • Europa orbiter – approved then eliminated in FY03 budget. May be revived pending NASA Outer Planets reorganization • Cassini mission to Saturn arrives July 2004. Will drop an ESA probe (Huygens) onto Titan, and flyby Titan and three smaller moons. • Pluto/Kuiper Express – Approved but not funded yet for FY03 - on hold pending NASA Outer Planets reorganization. Best case: arrival before 2020. Lynn Cominsky - Cosmology A350

39. Planetary Missions • 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. Lynn Cominsky - Cosmology A350

40. Planets around other stars Over 100 planets around other stars are known Lynn Cominsky - Cosmology A350

41. Planets around other stars • 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 Lynn Cominsky - Cosmology A350

42. Planets around other stars • 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 • 78 light years from Earth • 47 Ursae Majoris (Marcy and Butler 1996) • 1100 day orbit • 3 Jupiter masses • temperature of planet may allow liquid water to exist • 44 light years from Earth Lynn Cominsky - Cosmology A350

43. 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 Lynn Cominsky - Cosmology A350

44. 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 Lynn Cominsky - Cosmology A350

45. Other methods: • Astrometry – measuring the exact position of a star as it wobbles Hipparcos was an ESA satellite operational from 1989-93 Lynn Cominsky - Cosmology A350

46. 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%) Lynn Cominsky - Cosmology A350

47. The first transiting planet • HD209548 – a visualization by Aurore Simonnet Lynn Cominsky - Cosmology A350

48. 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 Lynn Cominsky - Cosmology A350

49. 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: Lynn Cominsky - Cosmology A350

50. Latest news (1/8/03) • Transiting observation used to discover planet • Earlier searches preferentially found closer orbiting planets, more massive planets and eccentric orbits (“hot Jupiters”) Lynn Cominsky - Cosmology A350