The cosmic shoreline concept was introduced to separate #planets with #atmospheres from those without, by relating the cumulative X-ray and extreme-ultraviolet (XUV) instellation to the planetary escape velocity, using the Solar System planets to anchor the empirical relation. The #exoplanet community has since attempted to refine the cosmic shoreline to provide a consistent ranking or prioritisation tool for exoplanet observations – i.e., to quickly identify which small #planets are most likely to have retained an #atmosphere. In a new paper, astronomers use an empirical approach to refine the cosmic shoreline concept. The Empirical Exoplanet Cosmic Shoreline (EECS) exhibits a significantly steeper slope than previously theorized, while consistently categorising Solar System moons and dwarf planets according to their atmospheric properties. Applied to planets orbiting M dwarfs, the EECS suggests that a larger fraction retain atmospheres than predicted by classical models, but incorporating revised XUV fluence histories for low-mass M dwarfs reveals severe atmospheric vulnerability. #astronomy #astrobiology https://astrobiology.com/2026/06/an-empirical-determination-of-the-cosmic-shoreline-2.html Paper by Meni-Gallardo & Pallé (2026): https://arxiv.org/abs/2508.12865