Laura K. Schaefer

A planet the size of Neptune, but glowing white-hot. Beneath the clouds lies an ocean of magma capable of absorbing an entire hydrogen atmosphere. The new SEAMIST model is the first to trace how such dissolution changes a planet's fate from birth to old age. The big surprise is the mechanism of catastrophic boiling.

The JWST space telescope aimed its lens at the scorching rocky world 55 Cancri e, and spotted a dense gas envelope. But the cooler TRAPPIST-1 b, which orbits a dim red dwarf, showed no envelope: just bare rock. The picture came out upside down: hot planets hold onto atmospheres, while cooler ones lose them.