Simulation of the Spin Evolution of Some Selected Exoplanets and Inferences on Their Climate

In this work, using the simulator VPLanet, we analyze the spin evolution of some selected exoplanets due to the tidal interaction with their host star. For a rocky planet, two spin “conditions” are possible, the “trapped” rotation and the “fast” rotation, referring to the cases of achieved and non-achieved tidal trapping, respectively. We focus on planets whose spin condition is not obvious, because no study is needed for planets which are undoubtedly fast rotators or undoubtedly trapped rotators; moreover, we consider only exoplanets that are interesting from an astrobiological perspective. The current spin conditions of the considered planets are hypothesized, taking into account the age of the host star. Inferences regarding planetary climate and habitability—which is defined by the possibility of stably sustaining the liquid water on the surface—are also discussed. Results of this work show that Kepler-62f, Kepler-1126c, and Kepler-1544b are expected to be fast rotators regardless of the orbital eccentricity; the spin condition of Kepler-186f, Kepler-62e, and Kepler-442b cannot be determined without constraints on the eccentricity, which are currently unavailable; Kepler-440b is expected to be tidally trapped.