JWST catches star vaporizing the hottest rocky exoplanets | by Ethan Siegel | Starts With A Bang! | Feb, 2025

At extremely close distances to their stars, even rocky planets can be completely disintegrated. We’ve just caught our first one in action.

For planets, just like in real estate, the most important property they can possess is “location.” If you want to form a rocky planet, that’s no problem if you’re in the inner part of your stellar system: interior to the analogue of the asteroid belt in our own Solar System. Further out, beyond those frost lines, ices and other volatiles can dominate, giving rise to solid-surfaced worlds that are more akin to giant iceballs than to planets like Mercury, Venus, Earth, or Mars. However, if you venture too close to your parent star, it won’t just be ices and volatiles that get vaporized, but even the layers of the planet itself: atmosphere, crust, mantle, and even the core in the most extreme scenarios.

While “hot Jupiter” exoplanets were among the first planets beyond our Solar System ever discovered, only a few have been caught close enough to their parent stars that their atmospheres are in the process of evaporating. Even more rarely, planets have been caught being completely swallowed by their parent stars. But rocky planets, too, can have their contents evaporated away if they’re heated sufficiently: to conditions where even the heavy elements composing their solid surfaces and…