Detailed Calculations of the Efficiency of Planetesimal Accretion in the Core-Accretion Model -II: The effect of Saturn

TL;DR

This study refines the core-accretion model by including Saturn's gravitational effects, showing its influence on planetesimal scattering, accretion rates, and potential implications for planetary envelope composition.

Contribution

It advances previous models by incorporating Saturn's gravity, revealing its impact on planetesimal dynamics and planetary envelope enrichment during accretion.

Findings

Saturn's perturbation reduces planetesimal accretion rate.

Increased encounter velocities lead to more planetesimal break-up.

Late accretion may explain high-Z material enrichment in planetary envelopes.

Abstract

As part of our ongoing initiative on accurately calculating the accretion rate of planetesimals in the core-accretion model, we demonstrated in a recent article that when the calculations include the gravitational force of the Sun (the original core-accretion model did not include solar gravity), results change considerably [ApJ, 899:45]. In this paper, we have advanced our previous study by including the effect of Saturn. To maintain focus on the effect of this planet, and in order to be consistent with previous studies, we did not include the effect of the nebular gas. Results demonstrated that as expected, Saturn's perturbation decreases the rate of accretion by scattering many planetesimals out of Jupiter's accretion zone. It also increases the velocities with which planetesimals encounter the envelope, which in agreement with our previous findings, enhances their break-up due to the ram-pressure. Results also show that, because the effect of Saturn in scattering of planetesimals increases with its mass, this planet might not have played a significant role in the accretion of planetesimals by proto-Jupiter during the early stage of its growth. Finally, the late accretion of planetesimals, as obtained in our previous study, appears in our new results as well, implying that combined with the rapid in-fall of the gas, it can result in the mixing of material in the outer regions of the envelope which may explain the enhancement of the envelope's high-Z material.