Tidal dissipation and synchronization of the temperate exo-Earth LP 791-18d

TL;DR

This paper investigates the tidal evolution and rotation state of the exo-Earth LP 791-18d using creep tide theory, suggesting it is likely in synchronous rotation with a specific eccentricity threshold.

Contribution

It applies creep tide theory to analyze the tidal synchronization and energy dissipation of LP 791-18d, providing insights into its rotation state and eccentricity constraints.

Findings

LP 791-18d is likely in synchronous rotation.

A 3:2 spin-orbit resonance requires eccentricity ≥ 0.04.

Tidal energy dissipation is approximately 1 watt per square meter.

Abstract

The creep tide theory is used to explore several aspects of the tidal evolution of the planetary system of the M-star LP 791-18 . We discuss the early synchronization of the exo-Earth LP 791-18d and show that the trapping of its rotation in a 3:2 spin-orbit resonance would only have been possible if its eccentricity were approximately 0.04 or larger. The planet is likely in synchronous rotation. The perturbations of the other planets in the system do not allow the complete damping of the orbital eccentricity, and the resulting mechanical energy balance indicates that the tidal energy dissipated inside the planet may flow through the planetary surface at approximately 1 watt per square meter.