Contributed Talk - Splinter Exoplanets

Tuesday, 13 September 2022, 14:30   (SFG 1010 / virtual Exo)

Excitation of the obliquity of Earth-like planets via tidal forcing

Ema Valente and Alexandre Correia
CFisUC, Physics Department, Coimbra University, Portugal

Close-in planets undergo strong tidal interactions with the parent star that modify their spins and orbits. It is commonly assumed that the rotation of this planets is synchronous and the planet spin axis is aligned with the normal to the orbit (zero planet obliquity). Here we show that, for non-zero eccentricities, the rotation rate can be trapped in spin–orbit resonances that delay the evolution towards the synchronous state. More interestingly, we observe that capture in some spin–orbit resonances may also excite the obliquity to high values rather than damp it to zero. Depending on the system parameters, obliquities up to 80 degrees can be maintained throughout the entire lifetime of the planet. This unexpected behaviour is particularly important for Earth-like planets in the habitable zone of M-dwarf stars, as it may help to sustain temperate environments and thus more favourable conditions for life.