f10_oct19 - Ast 307 - Oct. 19 , 2010 Extrasolar Planets and...

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Ast 307 - Oct. 19 , 2010 Extrasolar Planets and Planetary Systems Outside the frost line, ice as well as rock could form small particles. More mass was available than in the inner solar system, so larger planets could form. The gravity of these larger planets was able to draw in and retain H and He. This provided much more mass, so Jupiter has about 300 times the mass of the Earth. Formation of the Jovian Planets Current Debate: which picture is correct? 1. Core accretion: Solid cores formed first, then their gravity drew in the light gases (H and He), or 2. Gravitational Instability: The disk develops lumps of gas, which collapse similarly as the original solar nebula (no rocky cores) Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/ The Chaotic Early Solar System Recent computer models are challenging earlier views that planets formed in an orderly way at their current locations These models suggest that the Jovian planets changed their orbits substantially, and that Uranus and Neptune could have changed places These chaotic motions could also explain a ‘spike’ in the number of impacts in the inner solar system ~3.8 Gyr ago The Moon and terrestrial planets were bombarded by planetesimals early in solar system history. Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/ The model predicts: 1.After formation, giant planet orbits were affected by gravitational ‘nudges’ from surrounding planetesimals 2.Jupiter and Saturn crossed a 1:2 orbital resonance (the ratio of orbital periods), which made their orbits more elliptical. This suddenly enlarged and tilted the orbits of Uranus and Neptune 3.Uranus / Neptune cleared away the planetesimals, sending some to the inner solar system causing a spike in impact rates
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This note was uploaded on 04/30/2011 for the course AST 317 taught by Professor Dinerstein during the Fall '10 term at University of Texas at Austin.

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f10_oct19 - Ast 307 - Oct. 19 , 2010 Extrasolar Planets and...

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