New Constraints on the M Dwarf Cosmic Shoreline from a Galaxy Far, Far Away

TL;DR

This paper investigates the existence of a cosmic shoreline separating terrestrial planets with and without atmospheres, using both galactic and extragalactic data, and finds evidence that M dwarf planets can retain atmospheres.

Contribution

It introduces a new approach by incorporating extragalactic survey data to define the M dwarf cosmic shoreline and atmosphere retention metrics.

Findings

M dwarf planets can retain atmospheres despite high stellar activity.

The M dwarf cosmic shoreline slope aligns with predictions for Sun-like stars.

Extraterrestrial survey data enhances understanding of atmosphere retention across galaxies.

Abstract

Whether there is a cosmic shoreline that divides terrestrial planets which have atmospheres from those that don't is one of the biggest open questions in exoplanet science. Most atmosphere searches have focused on terrestrial planets around M dwarf stars, since their smaller radii compared to sun-like stars boost planet atmosphere signals. However, the higher activity levels of M dwarfs might also entirely preclude atmosphere retention for their planets. In this work we present a new hope for defining an M dwarf cosmic shoreline, leveraging not only data from exoplanets in our own galaxy, but a comprehensive survey conducted by a commission of the Galactic Republic a long, long time ago in a galaxy far, far away. In this survey, we find definitive proof that M dwarf planets can retain atmospheres, and define an M dwarf cosmic shoreline whose slope agrees well with empirical predictions for Sun-like stars. We then define atmosphere retention metrics for the planets on the JWST Rocky Worlds DDT Targets Under Consideration list. Our analysis highlights the benefits of looking beyond the Milky Way for answers to some of the field's most pressing questions.