Do Rocky Exoplanets Retain Their Atmospheres?

The presence or absence of a planetary atmosphere is the outcome of a multi-billion-year-long struggle between the planet’s surface gravity, its outgassing rate, its magnetic field, and the stellar XUV and particle flux incident upon the world. The orbs found to transit nearby M-stars are more observationally accessible owing to the diminutive sizes and low luminosities of the central stars. However, recent work has demonstrated that these stars sustain high XUV fluxes for billions of years, much longer than the epoch of atmospheric production. With powerful infrared observatories in orbit and on the ground, we are now mapping the cosmic shoreline that separates airlines worlds from those with atmospheres, possibly even ones containing biosignature gases. Unlike their smaller cousins, Sun-like stars will reveal their planets and any life upon them only through imaging, and this demanding task will fall squarely on the shoulders of the Habitable Worlds Observatory.

Speaker: David Charbonneau, Harvard University