Interactions of planetesimals with protoplanetary atmospheres

We compute the interaction of planetesimals with the envelopes of growing giant planets that form by the "core-instability" mechanism. According to this mechanism, a core grows by the accretion of solid bodies in the solar nebula, and the growing core becomes progressively more effective in gravitationally contracting gas from the surrounding solar nebula into an envelope, until a "runaway" accretion of gas occurs. We compute the two-body trajectories of planetesimals through this envelope, including the effects of gravitational and gas-drag forces for the envelopes surrounding cores of different masses ranging from 1.1 to 16.8 Earth masses. Curves are computed which show the depth of penetration of various-sized planetesimals through these envelopes, as are cross-sections for capture of icy and rocky planetesimals. The implications for the formation of the giant planets by this sort of mechanism and its influence on their composition are discussed.