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T. Guillot, B. Gladman (OCA)
Interior models of Jupiter and Saturn show that they contain 10-40\rm\,M\oplus and 19-31\rm\,M\oplus of heavy elements (i.e. other than hydrogen and helium), respectively. Some of them are embedded into a central core, which is most probably the remnant of the initial planetary embryo, but a significant fraction is contained in the planetary envelope, and was captured during and after the planet formation. Spectroscopic observations of their atmospheres show that they are significantly enriched in heavy elements compared to the initial protosolar nebula.
We study the fate of planetesimals in the early Solar System, using the Duncan and Levison symplectic integrator. We show that this fate is sealed for about 80 to 90% of the planetesimals before 10\,Gyr of dynamic evolution, at a time when the young, extended protoplanets are able to grab planetesimals to much further distances than they are now. Using a 100\,M\oplus disk with a surface density proportional to a-2, we estimate that 5-8\rm\,Moplus, and 2-4\rm\,Moplus could hit 10\rm\,Moplus-protoplanetary cores of Jupiter and Saturn, respectively. This seems in good agreement with interior model constraints and core size estimates from runaway growth formation. The consequences for various formation scenarios will be discussed.