Tilting Planets During Planet Scattering

TL;DR

This paper proposes a mechanism where planet-planet scattering can temporarily induce spin-orbit resonances, leading to significant tilting of a planet's spin-axis and explaining observed misalignments.

Contribution

It introduces a novel explanation for spin-axis tilting during planet scattering through transient spin-orbit resonances, linking it to observed planetary system configurations.

Findings

Spin-orbit resonances can occur during planet scattering.

Such resonances can cause large spin-axis misalignments.

The mechanism explains observed high eccentricities and inclinations.

Abstract

Observational constraints on planet spin-axis has recently become possible, and revealed a system that favors a large spin-axis misalignment, a low stellar spin-orbit misalignment and a high eccentricity. To explain the origin of such systems, we propose a mechanism that could tilt the planet spin-axis during planet-planet scattering, which are natural outcomes of in-situ formation and disk migration. Specifically, we show that spin-orbit resonances could occur for a short time period during the scattering processes, and excite the misalignment of the planet spin-axis. This typically leads to planets with large spin-misalignment and a wide range of eccentricities and inclinations.