Gas capture by distant protoplanets and the formation of Jovian planets.

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To clarigy the formation processes of Jovian planets and the origin of their characters, we investigated (i) the static structure of the gas envelope covering a protoplanet and (ii) the collapse process of the unstable gas envelope and developed the simulation code describing (iii) the capture of the nebular gas by a protoplanet.Our main results are summarized as follows.(i) Static structure of the gas envolope covering a protoplanetThe structure of the gas envelope is mainly governed by the energy released in the envelope due to the accretion of planetesimals. Taking into account fragmention of incident planetesimals due to the dynamical pressure, we estimated the energy flux and obtained the static solution of the gas envelope. As a result, we showed that fragmentation of planetesimals fairly reduces the energy flux and the critical core mass and that the critical mass we obtained becomes 1/4 of the value obtained by the previous studies.(ii) The collapse process of the unstable gas envelopeNext, we performed simulations of the collapse of the unstable gas envelope, taking into account the infall of the nebular gas. Futhermore, we analized the dynamical instability of the collapsing gas. Then we showed that the oscillational instability and the mass ejection suggested by Wuchterl (1993) do not occur. Our results support the formation process proposed in Kyoto model.(iii) Capture of the nebular gas by a protoplanetUsing the results in (i) and (ii), we started the development of the new simulation code describing the capture of the nebular gas by a protoplanet. The previous study had a demerit that the way of the gas capture strongly depends on the algorism of the code. We are now developing the new code which can overcome the demerit.