Normally, a major portion of the atoms and molecules making up a planet are hidden in clouds or deep under the atmosphere. Think of Earth—most of the molecules that make up our planet, from the core to the surface, aren’t represented in the atmosphere. In contrast, KELT-9b "is so incredibly hot, all the atoms and molecules are uniformly mixed through the atmosphere," Kreidberg said. "We can therefore see the raw materials that the planet is made of. This planet is an unmatched laboratory for studying the building blocks of planet formation."