World Records
The Most Extreme Planets Ever Discovered: Heat, Speed, Diamonds, and Glass Rain
KELT-9b has a dayside temperature of about 4,600 K, as hot as a K-type star. It is one of thousands of exoplanets whose conditions force astronomers to invent new atmospheric chemistry: iron that condenses on a night side, glass-forming haze, orbits measured in hours, and worlds with no star at all. Here is what the records actually say, and what they do not.