Astronomers aimed JWST at the rocky exoplanet LHS 3844 b — a world orbiting another star, where a year lasts just 11 hours. The planet is tidally locked: one side always faces the star, with a permanent scorch of 770°C, while the night side is plunged into icy darkness. JWST captured heat from the blazing hemisphere and, using spectroscopy — splitting light into a rainbow of colors — teased out the surface composition. Each mineral leaves its own unique hue, like a glowing ember in a campfire.
The surface turned out to be dark and quartz-poor, more like basalt or olivine. Such material recalls cooled embers: maybe the planet was once hot and churning, but now its internal fire is stone dead. Volcanic gases — carbon dioxide and sulfur dioxide, the usual markers of a living mantle — are nowhere to be found. Even the sensitive JWST couldn’t spot a whiff of steaming fissures. This is a dead world where the geological furnace has gone out for good.
LHS 3844 b whips around its star in just 11 hours. Its dayside roasts at 770°C, while the nightside stays invisible — thermal emission comes only from the hot half.