Spin Dynamics of Extrasolar Giant Planets in Planet-Planet Scattering

TL;DR

This paper investigates how planet-planet scattering influences the spin evolution and obliquity of extrasolar giant planets, revealing significant spin-orbit coupling effects during dynamical interactions.

Contribution

It introduces a study of spin dynamics during planet-planet scattering, highlighting the role of stellar torque and spin-orbit coupling in shaping planetary obliquities.

Findings

Planets can develop significant obliquity due to scattering.

Stellar torque is the main driver of spin evolution.

Spin-orbit coupling causes dramatic spin changes during scattering.

Abstract

Planet-planet scattering best explains the eccentricity distribution of extrasolar giant planets. Past literature showed that the orbits of planets evolve due to planet-planet scattering. This work studies the spin evolution of planets in planet-planet scattering in 2-planet systems. Spin can evolve dramatically due to spin-orbit coupling made possible by the evolving spin and orbital precession during the planet-planet scattering phase. The main source of torque to planet spin is the stellar torque, and the total planet-plane torque contribution is negligible. As a consequence of the evolution of the spin, planets can end up with significant obliquity (the angle between a planet's own orbit normal and spin axis) like planets in our Solar System.