Planetary Migration

TL;DR

This paper reviews the evolution of planetary migration studies, highlighting how improved models and physics have revealed mechanisms that can halt or reverse migration, aligning it with planet formation theories.

Contribution

It provides a comprehensive overview of planetary migration processes, emphasizing recent advances in modeling and understanding migration halting mechanisms.

Findings

Migration can be halted or reversed by specific disc regions.

Slower migration for giant planets due to nonlinear disc interactions.

Migration influenced by disc physics and evolution, not just planet-disc interactions.

Abstract

Studies of planet migration derived from disc planet interactions began before the discovery of exoplanets. The potential importance of migration for determining orbital architectures being realised, the field received greater attention soon after the initial discoveries of exoplanets. Early studies based on very simple disc models indicated very fast migration times for low mass planets that raised questions about its relevance. However, more recent studies, made possible with improving resources, that considered improved physics and disc models revealed processes that could halt or reverse this migration. That in turn led to a focus on special regions in the disc where migration could be halted. In this way the migration of low mass planets could be reconciled with formation theories. In the case of giant planets which have a nonlinear interaction with the disc, the migration should be slower and coupled to the evolution of the disc. The latter needs to be considered more fully to make future progress in all cases. Here we are primarily concerned with processes where migration is connected with the presence of the protopolanetary disk. Migration may also be induced by disc-free gravitational interactions amongst planets or with binary companions. This is only briefly discussed here.