Habitability of Super-Earth Planets around Other Suns: Models including Red Giant Branch Evolution

TL;DR

This study models the habitability of super-Earth exoplanets, considering stellar evolution including the Red Giant Branch, and identifies water-rich planets as most likely to sustain life during stellar evolution.

Contribution

It introduces a comprehensive thermal evolution model incorporating stellar evolution and biogeochemical processes to assess habitability of super-Earths over stellar lifetimes.

Findings

Water worlds are most likely to sustain habitability beyond the main sequence.

Habitability is strongly influenced by planetary water content and stellar evolution.

The model identifies conditions under which super-Earths can support life during stellar evolution.

Abstract

The unexpected diversity of exoplanets includes a growing number of super- Earth planets, i.e., exoplanets with masses of up to several Earth masses and a similar chemical and mineralogical composition as Earth. We present a thermal evolution model for a 10 Earth mass planet orbiting a star like the Sun. Our model is based on the integrated system approach, which describes the photosynthetic biomass production taking into account a variety of climatological, biogeochemical, and geodynamical processes. This allows us to identify a so-called photosynthesis-sustaining habitable zone (pHZ) determined by the limits of biological productivity on the planetary surface. Our model considers the solar evolution during the main-sequence stage and along the Red Giant Branch as described by the most recent solar model. We obtain a large set of solutions consistent with the principal possibility of life. The highest likelihood of habitability is found for "water worlds". Only mass-rich water worlds are able to realize pHZ-type habitability beyond the stellar main-sequence on the Red Giant Branch.