“A newly discovered Jupiter-like world is so hot, it’s being vaporized by its own star. With a dayside temperature of more than 7,800 degrees Fahrenheit (4,600 Kelvin), KELT-9b is a planet that is hotter than most stars. But its blue A-type star, called KELT-9, is even hotter — in fact, it is probably unraveling the planet through evaporation. “This is the hottest gas giant planet that has ever been discovered,” said Scott Gaudi, astronomy professor at The Ohio State University in Columbus, who led a study on the topic. He worked on this study while on sabbatical at NASA’s Jet Propulsion Laboratory, Pasadena, California. The unusual planet is described in the journal Nature and at a presentation at the American Astronomical Society summer meeting this week in Austin, Texas. KELT-9b is 2.8 times more massive than Jupiter, but only half as dense. Scientists would expect the planet to have a smaller radius, but the extreme radiation from its host star has caused the planet’s atmosphere to puff up like a balloon. Because the planet is tidally locked to its star — as the moon is to Earth — one side of the planet is always facing toward the star, and one side is in perpetual darkness. Molecules such as water, carbon dioxide and methane can’t form on the dayside because it is bombarded by too much ultraviolet radiation. The properties of the nightside are still mysterious — molecules may be able to form there, but probably only temporarily.”