This Exoplanet Is So Hot, It Might Be Evaporating

Kelt-9b and its parent star, which heats its surface to temperatures nearly as hot as the sun. (Credit: NASA/JPL-Caltech/R. Hurt (IPAC)) Astronomers recently announced the discovery of the hottest known giant exoplanet. Sitting 650 light years away in the constellation Cygnus, Kelt-9b is a scorching ball of gas roughly three times the size of Jupiter. Temperatures there are estimated to reach 7,800 degrees Fahrenheit, hot enough that the planet's atmosphere may be evaporating away into space, leaving a comet-like tail in its wake. Kelt-9b is so hot thanks to an extremely close-in orbit that takes it around its star just once every 36 hours. It's near enough that it will eventually be engulfed by its star, Kelt-9, when it reaches the end of its life and begins to expand as a red giant. Kelt-9 is about twice as large and hot as our sun, and this planet is one of ...