Detailed Calculations of the Efficiency of Planetesimal Accretion in the Core-Accretion Model -III: The Contribution of Planetesimals Beyond Saturn

TL;DR

This study extends previous calculations of planetesimal accretion in the core-accretion model by analyzing the contribution of planetesimals beyond Saturn, finding their impact on Jupiter's growth to be minimal and highlighting the correlation between accretion rate and envelope evolution.

Contribution

It expands the distribution of planetesimals considered to regions beyond Saturn and demonstrates that exterior planetesimals have little effect on Jupiter's final mass and composition.

Findings

Exterior planetesimals beyond 8 AU contribute minimally to Jupiter's growth.

Final Jupiter mass is mainly determined by planetesimals near its accretion zone.

Accretion rate peaks during the envelope's collapse phase.

Abstract

Continuing our initiative on advancing the calculations of planetesimal accretion in the core-accretion model, we present here the results of our recent study of the contributions of planetesimals around and beyond the orbit of Saturn. In our first two papers [ApJ, 899:45; 941:117], where our focus was on the effects of the Sun and Saturn, the initial distribution of planetesimals was limited to the regions around the accretion zone of a growing Jupiter. In this paper, we expanded that distribution to regions beyond the accretion zone of Saturn. We integrated the orbits of a large ensemble of planetesimals and studied the rate of their capture by the growing proto-Jupiter. In order to be consistent with our previous studies, we did not consider the effect of the nebular gas. Results demonstrated that the exterior planetesimals, especially those beyond 8 AU, have only slight contributions to the growth and metallicity of the growing Jupiter. The final mass and composition of this planet is mainly due to the planetesimals inside and around its accretion zone. Our study shows that although the rate of capture varies slightly by the size and composition of planetesimals, in general, the final results are independent of the size and material of these bodies. Results also pointed to a new finding: the rate of accretion follows the same trend as that of the evolution of Jupiter's envelope, with the largest accretion occurring during the envelope's collapse. We present details of our analysis and discuss the implications of their results.