Physical constraints on the likelihood of life on exoplanets

TL;DR

This paper assesses the physical factors influencing exoplanet habitability, revealing that Earth-sized planets around M-dwarfs have significantly lower likelihoods of supporting life due to stellar radiation and atmospheric loss.

Contribution

It introduces a quantitative framework to estimate exoplanet habitability based on physical constraints like temperature and atmospheric escape, applied to recent exoplanets.

Findings

Earth-sized planets around M-dwarfs have lower habitability prospects.

Proxima b and TRAPPIST-1e have much smaller likelihoods of supporting life than Earth.

Physical constraints significantly impact exoplanet habitability assessments.

Abstract

One of the most fundamental questions in exoplanetology is to determine whether a given planet is habitable. We estimate the relative likelihood of a planet's propensity towards habitability by considering key physical characteristics such as the role of temperature on ecological and evolutionary processes, and atmospheric losses via hydrodynamic escape and stellar wind erosion. From our analysis, we demonstrate that Earth-sized exoplanets in the habitable zone around M-dwarfs seemingly display much lower prospects of being habitable relative to Earth, owing to the higher incident ultraviolet fluxes and closer distances to the host star. We illustrate our results by specifically computing the likelihood (of supporting life) for the recently discovered exoplanets, Proxima b and TRAPPIST-1e, which we find to be several orders of magnitude smaller than that of Earth.