Orbital Migration through Atmospheric Mass Loss

TL;DR

This paper presents a simple model showing that anisotropic atmospheric mass loss driven by stellar winds can cause small but potentially observable inward orbital migration of close-in exoplanets, offering new insights into planetary evolution.

Contribution

It introduces a kinematic model linking atmospheric mass loss anisotropy to planetary migration, highlighting a novel mechanism for orbital evolution due to stellar wind effects.

Findings

Typical inward migration of a few tenths to a few percent.

Migration may be detectable in planet pairs near mean motion resonances.

Provides a potential observational constraint on atmospheric mass loss models.

Abstract

Atmospheric mass loss is thought to have strongly shaped the sample of close-in exoplanets. These atmospheres should be lost isotropically, leading to no net migration on the planetary orbit. However, strong stellar winds can funnel the escaping atmosphere into a tail trailing the planet. We derive a simple kinematic model of the gravitational interaction between the planet and this anisotropic wind, and derive expressions for the expected migration of the planet. Over the expected range of parameters, we find typical migrations of a few tenths to a few percent inward. We argue that this modest migration may be observable for planet pairs near mean motion resonances, which would provide an independent observational constraint on atmospheric mass loss models.