Outward Migration of Jupiter and Saturn in Evolved Gaseous Disks

TL;DR

This study investigates the conditions under which Jupiter and Saturn-like planets can migrate outward in evolved gas disks, using hydrodynamical simulations to understand the influence of disk properties and resonances on their orbital evolution.

Contribution

It provides a detailed analysis of the mechanisms and conditions that enable outward migration of giant planets in evolved protoplanetary disks, highlighting the roles of mean motion resonances and disk parameters.

Findings

Outward migration occurs mainly in the 3:2 resonance under specific disk conditions.

Resonance locking does not always lead to outward migration, especially in the 2:1 resonance.

Only a small percentage of models predict planets reaching beyond 4 AU.

Abstract

The outward migration of a pair of resonant-orbit planets, driven by tidal interactions with a gas-dominated disk, is studied in the context of evolved solar nebula models. The planets' masses, M1 and M2, correspond to those of Jupiter and Saturn. Hydrodynamical calculations in two and three dimensions are used to quantify the migration rates and analyze the conditions under which the outward migration mechanism may operate. The planets are taken to be fully formed after 1e6 and before 3e6 years. The orbital evolution of the planets in an evolving disk is then calculated until the disk's gas is completely dissipated. Orbital locking in the 3:2 mean motion resonance may lead to outward migration under appropriate conditions of disk viscosity and temperature. However, resonance locking does not necessarily result in outward migration. This is the case, for example, if convergent migration leads to locking in the 2:1 mean motion resonance, as post-formation disk conditions seem to suggest. Accretion of gas on the planets may deactivate the outward migration mechanism by raising the mass ratio M2/M1 and/or by reducing the accretion rate toward the star, hence depleting the inner disk. For migrating planets locked in the 3:2 mean motion resonance, there are stalling radii that depend on disk viscosity and on stellar irradiation, when it determines the disk's thermal balance. Planets locked in the 3:2 orbital resonance that start moving outward from within 1-2 AU may reach beyond 5 AU only under favorable conditions. However, within the explored space of disk parameters, only a small fraction - less than a few per cent - of the models predict that the interior planet reaches beyond 4 AU.