The tidal heating of the exoplanet 55 Cnc e

Abstract

Context. Observations with warm Spitzer and JWST have revealed a high and variable brightness in the planet 55 Cnc e.Aims. Our aim is to make an inventory of the tidal effects on the rotational and orbital evolution of the planet 55 Cnc e enhanced by the nonzero orbital eccentricity.Methods. The creep-tide theory is used in simulations and dynamical analyses that explore the difficult trapping of the planet’s rotation in a 3:2 spin-orbit resonance and the most probable synchronization of the rotation.Results. The strong tidal dissipation of energy, enhanced by the nonzero orbital eccentricity, may explain the observed brightness anomalies. However, the strong dissipation should also circularize the orbit. The observed nonzero eccentricity, if true, would indicate that an unknown planet in a close orbital resonance with 55 Cnc e perturbing the motion of this planet should exist.