1. Universe Seventh Edition Chapter 8: Comparative Planetology II: The Origin of Our Solar System Copyright © 2005 by W. H. Freeman & Company Roger A. Freedman and William J. Kaufmann III

3. Solar System attributes Rocky, small terrestrial planets, Gaseous (hydrogen and helium), giant jovian planets Planets orbit sun in the same direction Terrestrial planets orbit closer than jovian planets

4. Abundances & heavy elements Hydrogen and helium 98%, heavy elements 2% Why? Big bang formed lighter elements and stars produced heavier elements. Smaller abundances means smaller planets (Item 1)

8. Radioactive dating and the age of Solar System Radioactivity Rocks on Earth ~ 4 billion years Rocks on moon ~ 4 billion years Meteorites ~ 4 billion years Hence, Solar system age ~ 4 billion years !!!

11. Proto planetary disk Gravitational energy of contracting gas to thermal energy is “Kelvin- Helmholtz contraction”

12. Item 2: Planets orbit sun in the same direction

15. Planets formed by accretion of planetesimals and gases For a given pressure, “condensation temperature” determines gas or solid phase. Water, methane, ammonia ~ 100 K Rocky substances ~ 1500 K Hydrogen, helium ~ 0K So hydrogen and helium always are in gas phase.

18. Planetesimals: Chunks of rocks coalesced to form asteroidlike objects (~ 1 km) Protoplanets: Planetesimals collided to form moon size objects.

21. Chemical Differentiation Core accretion of outer planets

24. The gravity of Jovian planets sent most of the asteroids either away from SS or crashed into planets to form craters. Kuiper belt objects ( ex : pluto) formed beyond jupiter but sent away farther by gravity. Some went even as far as 50,000 AU and formed “Oort cloud”. Comets come from Kuiper belt or Oort cloud

25. T Tauri wind

27. Extrasolar planets