Migration of Protoplanets in Radiative Disks

TL;DR

This paper investigates how radiative effects in protoplanetary disks influence planet migration, showing that small planets can migrate outward, which may resolve issues with rapid inward migration in planet formation models.

Contribution

The study provides detailed numerical simulations demonstrating that radiative processes can reverse or slow inward migration for small planets, a novel insight into planet-disk interactions.

Findings

Small planets (<50 Earth masses) migrate outward in radiative disks.

Larger planets (>50 Earth masses) migrate inward, similar to isothermal models.

Radiative effects can mitigate rapid inward migration during early planet growth.

Abstract

In isothermal disks the migration of protoplanets is directed inward. For small planetary masses the standard type-I migration rates are so fast that this may result in an unrealistic loss of planets into the stars. We investigate the planet-disk interaction in non-isothermal disks and analyze the magnitude and direction of migration for an extended range of planet masses. We have performed detailed two-dimensional numerical simulations of embedded planets including heating/cooling effects as well as radiative diffusion for realistic opacities. In radiative disks, small planets with M_planet < 50 M_Earth do migrate outward with a rate comparable to absolute magnitude of standard type-I migration. For larger masses the migration is inward and approaches the isothermal, type-II migration rate. Our findings are particularly important for the first growth phase of planets and ease the problem of too rapid inward type-I migration.