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Planetesimal Capture as a Clue to the Formation of Gas-Giants

Haghighipour, N (Hawaii)
Tuesday 10 November 2009, 12:40-13:00



Prior to the last stage of the formation of a giant planet, the core of this object is surrounded by an extended gaseous envelope. The models of giant planet formation suggest that, to the first order, this envelope should have a strictly solar composition. However, measurements by Galileo spacecraft have indicated a higher-than-solar abundance of heavy elements in the atmosphere of Jupiter. During giant planet formation, the Solar System is populated by km-sized and larger bodies, many of which may scatter into the giant planet's proto-atmosphere where their dynamics is affected by gas drag. As a result, these objects may be captured entirely, or may deposit some of their materials in passing through the envelope. We have studied the interactions of planetesimals with the gaseous envelope of an evolving giant planet, and have computed the efficiency of their capture and of the deposition of different elements. We present the results of our study and discuss the relation between the physical and dynamical properties of planetesimals, and the rate of their mass deposition. Since a planet formed by the disk instability scenario will have very different capture cross-sections over time than a planet formed by the core accretion model, our study should help to differentiate between these two scenarios, as well.

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