The Hottest Planet in the Galaxy Is Hotter Than a Star

Somewhere out there is a planet so hot it's hotter than many actual stars.

It's called KELT-9b, a giant gas world about 670 light-years away, with a dayside temperature around 4,300 degrees Celsius.

KELT-9b orbits scorchingly close to a large, blue-white star, whipping around it in just a day and a half. It's so close that the heat is brutal, hotter than the surface of many smaller, cooler stars. At that temperature, the planet can't even hold normal molecules together. The intense radiation rips water and other molecules apart. The planet is also slowly evaporating, trailing material as its star blasts it with relentless light. It's tidally locked too, so one side roasts in permanent day while the other faces eternal night.

Think about that. We tend to imagine stars as hot and planets as cool. But this world flips that idea completely. Out in the galaxy, there's a planet that out-burns the very stars we compare it to.

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