Spin Dynamics of Extrasolar Giant Planets in Planet-Planet Scattering

Planet-planet scattering best explains the eccentricity distribution of extrasolar giant planets, and 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 two-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 planet-planet torque contribution is negligible. As a consequence of the evolution of the spin, planets can end up with appreciable obliquities (the angle between a planet's own orbit normal and spin axis), with the obliquity distribution peaking at about 10 degrees, and extending to much larger values.

Automated summary

The study indicates that planet-planet scattering can cause the spin of planets to evolve, resulting in potentially large obliquities. The evolution of planet spin is mainly influenced by the torque from the central star.