Planetary Core Formation with Collisional Fragmentation and Atmosphere to Form Gas Giant Planets

TL;DR

This paper explores how planetary cores grow to become gas giants by considering collisional fragmentation and atmospheric effects, showing that large initial planetesimals in massive disks facilitate core growth within disk lifetimes.

Contribution

It introduces a model combining collisional fragmentation and atmospheric growth effects, demonstrating conditions for forming massive cores in planet formation.

Findings

Atmospheric growth accelerates core formation after Mars mass.

Large initial planetesimals in massive disks enable core growth within disk lifetime.

Fragmentation reduces available planetesimals, affecting core mass accumulation.

Abstract

Massive planetary cores ($\sim 10$ Earth masses) trigger rapid gas accretion to form gas giant planets \rev{such as} Jupiter and Saturn. We investigate the core growth and the possibilities for cores to reach such a critical core mass. At the late stage, planetary cores grow through collisions with small planetesimals. Collisional fragmentation of planetesimals, which is induced by gravitational interaction with planetary cores, reduces the amount of planetesimals surrounding them, and thus the final core masses. Starting from small planetesimals that the fragmentation rapidly removes, less massive cores are formed. However, planetary cores acquire atmospheres that enlarge their collisional cross section before rapid gas accretion. Once planetary cores exceed about Mars mass, atmospheres significantly accelerate the growth of cores. We show that, taking into account the effects of fragmentation and atmosphere, initially large planetesimals enable formation of sufficiently massive cores. On the other hand, because the growth of cores is slow for large planetesimals, a massive disk is necessary for cores to grow enough within a disk lifetime. If the disk with 100\,km-sized initial planetesimals is 10 times as massive as the minimum mass solar nebula, planetary cores can exceed 10 Earth masses in the Jovian planet region ($>5\,$AU).