Potential Interior Structures and Habitability of Super-Earth Exoplanets LHS 1140 b, K2-18 b, TOI-1452 b and TOI-1468 c

TL;DR

This study models the internal structure and assesses the habitability of four nearby super-Earth exoplanets orbiting M-dwarf stars, considering tidal and atmospheric heating effects to identify potential habitable conditions.

Contribution

It introduces a Bayesian interior modeling approach combined with analytical climate models to evaluate habitability of these exoplanets.

Findings

K2-18 b and TOI-1468 c are likely water worlds with thin atmospheres.

TOI-1452 b and LHS 1140 b may have rocky surfaces and potential habitability.

Tidal heating alone is insufficient for surface warming; greenhouse effects are crucial.

Abstract

We analyze four super-Earth exoplanets, LHS 1140 b, K2-18 b, TOI-1452 b, and TOI-1468 c, which orbit M-dwarf stars in the habitable zone. Their relative proximity, within 40 parsecs, makes them prime candidates for follow-up observations and atmospheric and habitability studies. This paper aims to assess their internal structure and habitability, considering their tidal heating, atmospheric heating, and global transport. We model the interior structure of the planets by applying Bayesian inference to an exoplanet's interior model. A constant quality factor model is used to calculate the range of tidal heating, and a one-dimensional analytical model of tidally locked planets is used to assess their surface temperature distribution and habitability. Assuming no or only thin atmospheres, K2-18 b and TOI-1468 c are likely to be water worlds. However, TOI-1452 b and LHS 1140 b may have rocky surfaces. We find that tidal heating is not enough to raise the global mean surface temperature, but greenhouse heating can effectively do so. If the considered planets have retained thick atmospheres, K2-18 b, TOI-1468 c, and TOI-1452 b may, for significant atmospheric heating and heat transport factors, be too hot to sustain liquid water on their surface. However, the lower instellation of LHS 1140 b and the non-zero probability of it having a rocky surface give more space for habitable conditions on the planet.