Spin-orbit resonances and rotation of coorbital bodies in quasi-circular orbits

TL;DR

This paper demonstrates that coorbital bodies in quasi-circular orbits can exhibit stable non-synchronous rotation and chaos, challenging the assumption that dissipation always leads to synchronous rotation in such systems.

Contribution

It reveals that coorbital bodies can maintain non-synchronous rotation and experience chaos, even in nearly circular orbits, due to the interplay of libration frequencies and asymmetries.

Findings

Stable non-synchronous rotation is possible in coorbital systems.

Rotation can become chaotic when libration frequencies match.

Dissipation does not always lead to synchronous rotation.

Abstract

The rotation of asymmetric bodies in eccentric Keplerian orbits can be chaotic when there is some overlap of spin-orbit resonances. Here we show that the rotation of two coorbital bodies (two planets orbiting a star or two satellites of a planet) can also be chaotic even for quasi-circular orbits around the central body. When dissipation is present, the rotation period of a body on a nearly circular orbit is believed to always end synchronous with the orbital period. Here we demonstrate that for coorbital bodies in quasi-circular orbits, stable non-synchronous rotation is possible for a wide range of mass ratios and body shapes. We further show that the rotation becomes chaotic when the natural rotational libration frequency, due to the axial asymmetry, is of the same order of magnitude as the orbital libration frequency.