Dynamics of exoplanetary systems, links to their habitability

TL;DR

This paper explores how tidal interactions and orbital dynamics in exoplanetary systems, especially around brown dwarfs, influence planetary habitability by affecting climate, internal heating, and potential for surface liquid water.

Contribution

It investigates the impact of tides and planet-planet interactions on exoplanet habitability, highlighting the case of planets around brown dwarfs and the evolutionary state of Kepler-186f.

Findings

Eccentricity excitation by planet-planet interactions causes internal heating.

Tidal heating can prevent habitable surface conditions.

The evolutionary state of Kepler-186f affects its climate and habitability.

Abstract

Our knowledge of planets' orbital dynamics, which was based on Solar System studies, has been challenged by the diversity of exoplanetary systems. Around cool and ultra cool dwarfs, the influence of tides on the orbital and spin evolution of planets can strongly affect their climate and their capacity to host surface liquid water. We illustrate the role of tides and dynamics with the extreme case of planets orbiting around brown dwarfs. In multiple planet systems, the eccentricity is excited by planet-planet interactions. Planets are therefore heated up from the inside by the tidally-induced friction. This process can heat a habitable zone planet to such a level that surface liquid water cannot exist. We also talk about the newly discovered potentially habitable Earth-sized planet Kepler-186f. Given the poorly estimated age of the system, the planet could still be evolving towards synchronization and have a high obliquity or be pseudo-synchronized with a zero obliquity. These two configurations would have a different effect on the climate of this planet.