Tidal Evolution Of Exoplanetary Systems Hosting Potentially Habitable Exoplanets. The cases of LHS-1140 b-c and K2-18 b-c LHS-1140 b-c

LHS-1140 b-c

We present a model to study secularly and tidally evolving three-body systems composed by two low-mass planets orbiting a star, in the case where the bodies rotation axes are always perpendicular to the orbital plane.

The tidal theory allows us to study the spin and orbit evolution of both stiff Earth-like planets and predominantly gaseous Neptune-like planets. The model is applied to study two recently-discovered exoplanetary systems containing potentially habitable exoplanets (PHE): LHS-1140 b-c and K2-18 b-c. For the former system, we show that both LHS-1140 b and c must be in nearly-circular orbits. For K2-18 b-c, the combined analysis of orbital evolution timescales with the current eccentricity estimation of K2-18 b allows us to conclude that the inner planet (K2-18 c) must be a Neptune-like gaseous body.

Only this would allow for the eccentricity of K2-18 b to be in the range of values estimated in recent works (e=0.20±0.08), provided that the uniform viscosity coefficient of K2-18 b is greater than 2.4×1019 Pa s (which is a value characteristic of stiff bodies) and supposing that such system has an age of some Gyr.

Gabriel O. Gomes, Sylvio Ferraz-Mello
Comments: 9 pages, 6 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference: Monthly Notices of the Royal Astronomical Society, Issue 4, June 2020, Pages 5082-5090
DOI: 10.1093/mnras/staa1110
Cite as: arXiv:2005.10318 [astro-ph.EP] (or arXiv:2005.10318v1 [astro-ph.EP] for this version)
Submission history
From: Gabriel De Oliveira Gomes
[v1] Wed, 20 May 2020 19:06:09 UTC (185 KB)

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