Cosmic Shoreline Archives

Schematic of the three atmospheric retention and loss regimes for close-in rocky planets.

An Evolving Cosmic Shoreline and Sandbar Bounding the Rocky Airless Valley

by Keith CowingAugust 27, 2026August 27, 2026

[astro-ph.EP] Recent JWST observations challenge the traditional ‘cosmic shoreline’ from both sides, revealing thick volatile atmospheres on the hottest close-in ‘lava worlds,’ where irradiation should drive the most extreme escape, […]

The Cosmic Shoreline. Light-green dots are all known exoplanets with reported atmospheric detections from the ExoAtmospheres database, noting that some of these detections are tentative or remain contested in the literature (e.g., GJ 1132 b). Solar System objects are marked as black crosses or green triangles if they host an atmosphere. The red dashed line is the cosmic shoreline as defined by Zahnle & Catling (2017). The black dotted is the same classical line, preserving the slope, but taking as zero point the exoplanet 55 Cnc e. The black dashed-dotted line is our newly proposed Empirical Exoplanet Cosmic Shoreline (EECS), which makes use of both Mars and several exoplanet atmospheric detections to define the slope and zero-point value. The numbers highlighted in the inset show the names of the seven planets discussed in the definition of the EECS. -- astro-ph.EP

Uncategorized

An Empirical Determination Of The Cosmic Shoreline

by Keith CowingJune 23, 2026June 23, 2026

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 (integrated over the planet’s lifetime) to the […]

Radial velocity data for GJ 3378. Top: the combined RV time series. The orbit model is shown as a dashed line. Middle: RV residuals to a 1-planet model. Bottom: RVs phase-folded to the period of the exoplanet. Phase-binned RVs are shown as squares. -- astro-ph.EP

Astronomy & Telescopes, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Press Release

A Revised Mass and Period for the Habitable Zone super-Earth GJ 3378b: A Planet Straddling the Cosmic Shoreline

by Keith CowingMay 19, 2026May 19, 2026

The nearby (d=7.7 pc) M4V star GJ~3378 is a target of our radial velocity (RV) exoplanet survey of fully convective stars in the Solar neighborhood with the near-infrared spectrograph HPF […]

Multi-color ground-based light curves for our five targets. Data points represent 10-minute binned photometry, with light curves obtained using identical filters and exposure times phase-folded together. Black curves show the median transit model derived from the posterior distribution, with colored shading indicating the 68% confidence intervals. Blue curves represent the nominal TESS light curve model projected into the corresponding ground-based filters. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

From Earths To Super-Earths: Five New Small Planets Transiting M Dwarf Stars

by Keith CowingDecember 18, 2025December 18, 2025

Earth-sized planets transiting M dwarf stars present one of the best opportunities with current facilities for studying the atmospheric and bulk compositions of terrestrial worlds.

Position of TOI-270 b relative to the cosmic shoreline.

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Possible Evidence For The Presence Of Volatiles On The Warm Super-Earth TOI-270 b

by Keith CowingSeptember 18, 2025September 18, 2025

The search for atmospheres on rocky exoplanets is a crucial step in understanding the processes driving atmosphere formation, retention, and loss.

Cosmic Shoreline for all known planetary systems orbiting M-dwarf-type stars. The black dashed-dotted line is our newly proposed Empirical Cosmic Shoreline (ECS), same as in Figure 1. The gray points mark the systems whose atmospheres have not been studied; the orange ones mark the planets with reported strong non-detections; and the green ones mark the planets with a (tentative) atmosphere detection. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report, Stellar Cartography

An Empirical Determination Of The Cosmic Shoreline

by Keith CowingAugust 19, 2025August 19, 2025

The Cosmic Shoreline concept was introduced as a way to separate planets with and without atmosphere, based on the relationship between the cumulative instellation and the escape velocity observed in […]

A cosmic shoreline dividing exoplanets (errorbars) and Solar System planets (squares) with any type of atmosphere or global surface volatiles (blue symbols, Ai = 1) from those without (brown symbols, Ai = 0). Planets without definitive atmosphere constraints are shown for context (gray symbols, Ai =?). The shoreline defines a plane in the 3D space of (f, vesc, L); each row shows slices that consider a narrow range of stellar luminosity (top), planet escape velocity (middle), and planet flux (bottom). Background colors indicate the modeled probability of an atmosphere at each location (sandy brown for pi = 0, water blue for pi = 1), accounting for the intrinsic width of the shoreline and marginalizing over the parameter uncertainties and the width of the slice; contours (dashed lines) highlight atmosphere probabilities of 5%, 50%, 95% (). -- astro-ph.EP

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report

The 3D Cosmic Shoreline For Nurturing Planetary Atmospheres

by Keith CowingJuly 7, 2025July 7, 2025

Various “cosmic shorelines” have been proposed to delineate which planets have atmospheres. The fates of individual planet atmospheres may be set by a complex sea of growth and loss processes, […]

Astrochemistry, Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Press Release

JWST Thermal Emission of the Terrestrial Exoplanet GJ 1132b

by Keith CowingAugust 28, 2024August 27, 2024

We present thermal emission measurements of GJ 1132b spanning 5–12 um obtained with the Mid-Infrared Instrument Low-Resolution Spectrometer (MIRI/LRS) on the James Webb Space Telescope (JWST).