Day N Nite: Habitability of Tidally-Locked Planets with Sporadic Rotation

TRAPPIST-1 has 7 Earth-size exoplanets in close proximity that are in resonance. N-body simulations show that these planets can experience relatively large eccentricity and mean motion variations. Most studies and discussions of these planets’ climates assume these planets are always tidally locked, as are many other M-dwarf, habitable-zone planets with short orbital periods. However, large eccentricity and mean motion variations in TRAPPIST-1 can lead to sporadic rotation of the planets with synodic rotation periods on the order of years. I conduct N-body simulations using REBOUND to retrieve the evolution of orbital parameters in the TRAPPIST-1 system. The orbital parameters are used to produce a continuous equation of motion which describes the evolution of the substellar longitude and, thus, the hemisphere illuminated by the star. I will discuss the nature of these planets that transition between tidally-locked and slow rotation states, the origin of these transitions in TRAPPIST-1’s unique orbital dynamics, and the impact on climate using EBM models.