Outward Migration of Super-Jupiters

TL;DR

This paper demonstrates that super-Jupiters can migrate outward in protoplanetary disks due to disk eccentricity effects, challenging previous inward migration models and explaining their observed large orbital distances.

Contribution

The study shows that higher-mass planets can migrate outward due to disk eccentricity effects, differing from prior inward migration predictions.

Findings

Super-Jupiters can migrate outward in disks with certain conditions.

The transition from inward to outward migration aligns with disk eccentricity changes.

Outward migration may explain the large distances of observed super-Jupiters.

Abstract

Recent simulations show that giant planets of about one Jupiter mass migrate inward at a rate that differs from the Type II prediction. Here we show that at higher masses, planets migrate outward. Our result differs from previous ones because of our longer simulation times, lower viscosity, and our boundary conditions that allow the disk to reach viscous steady state. We show that, for planets on circular orbits, the transition from inward to outward migration coincides with the known transition from circular to eccentric disks that occurs for planets more massive than a few Jupiters. In an eccentric disk, the torque on the outer disk weakens due to two effects: the planet launches weaker waves, and those waves travel further before damping. As a result, the torque on the inner disk dominates, and the planet pushes itself outward. Our results suggest that the many super-Jupiters observed by direct-imaging at large distances from the star may have gotten there by outward migration.