Here in our own planetary system, humanity has spent the vast majority of its time studying planets that are rather chilly. Jupiter, Saturn, and even Mars range from cold to downright frigid. But now, researchers have discovered an exoplanet so unbelievably hot that it’s actually really difficult to even imagine it. It’s a world known as KELT-9b, and it’s so steamy that its atmosphere is hotter than many stars.
The planet, which is a gas giant, orbits its star so closely that it manages to complete an entire orbit in just one and a half Earth days, which is nearly 250 times faster than the Earth takes to get around our sun. Because of its close proximity, it’s tidally locked to its star, with a distinct “day side” that is always facing the extreme heat source.
KELT-9b’s atmosphere is thought to be in the neighborhood of 7,800 degrees Fahrenheit. That’s a number so high it’s hard to really put in perspective, but just for reference, normal glass melts at between 1,000 and 1,500 degrees Fahrenheit, while steel melts at around 2,750 degrees Fahrenheit. KELT-9b is almost three times hotter than that.
The star that the planet orbits is hotter than our own, and it’s putting KELT-9b in a pretty tough spot. The gas giant is so close, hot, and under such a radiation bombardment from its star that it could ultimate destroy it entirely. “KELT-9 radiates so much ultraviolet radiation that it may completely evaporate the planet,” Keivan Stassun of Vanderbilt University said in a statement. “Or, if gas giant planets like KELT-9b possess solid rocky cores as some theories suggest, the planet may be boiled down to a barren rock, like Mercury.”
