Core Formation and Heavy Element Enrichment in Giant Gaseous
Protoplanets
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 stellar composition and no core. However, the final composition and core mass of the planet can change 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.), and the planet's radial distance from the star. Silicate grains in low mass protoplanets (< 5 M_Jupiter) can sediment to the planets center and form cores. Implications of the results to Jupiter, Saturn, and extra-solar giant planets will be discussed.