Dynamics of Rotation of Super-Earths

TL;DR

This study uses numerical methods to analyze the rotational dynamics of close-in super-Earths, revealing how parameters like eccentricity can induce chaotic rotation states near synchronization.

Contribution

It introduces a detailed numerical exploration of super-Earth rotation dynamics considering asymmetric shapes and tidal effects, highlighting the potential for chaotic rotation states.

Findings

Rotation can be strongly perturbed by system parameters.

Chaotic layers around synchronous rotation can be significant.

Eccentricity critically influences rotation stability.

Abstract

We numerically investigate the dynamics of rotation of several close-in terrestrial exoplanet candidates. In our model, the rotation of the planet is disturbed by the torque of the central star due to the asymmetric equilibrium figure of the planet. We model the shape of the planet by a Jeans spheroid. We use surfaces of section and spectral analysis to explore numerically the rotation phase space of the systems adopting different sets of parameters and initial conditions close to the main spin-orbit resonant states. One of the parameters, the orbital eccentricity, is critically discussed here within the domain of validity of orbital circularization timescales given by tidal models. We show that, depending on some parameters of the system like the radius and mass of the planet, eccentricity etc, the rotation can be strongly perturbed and a chaotic layer around the synchronous state may occupy a significant region of the phase space. 55 Cnc e is an example.