event
Tuesday 16 Jun 2009: Heavy Element Enrichment and Core Formation in Giant Gaseous Protoplanets
Dr Ravit Helled - University of California
Physics, 4th Floor interaction area 12:00-13:00
One possible mechanism for giant planet formation is disk instability in which the planet is formed as a result of gravitational instability in the protoplanetary disk surrounding the young star. A protoplanet formed in this model starts with a solar composition and no core. However, the final composition and core mass of the planet can change considerably due to the processes of planetesimal accretion and grain sedimentation. A gas giant protoplanet can capture a large fraction of the solid material in its feeding zone, leading to a significant enrichment in heavy elements. The final composition of the planet will depend on its mass, its 'birth environment' (disk mass, density profile, etc.), the planetesimal accretion efficiency, and the planet's radial distance from the star. This model explains the large variation in heavy element enrichment found in extra-solar giant planets. I will show that silicate grains in low mass protoplanets (< 5 M_Jupiter) can sediment to the planetary centers and form cores. Implications of the results to extra-solar giant planets, Jupiter, and Saturn will be discussed.
