‘Hottest’ planet in universe discovered

This artist’s concept shows planet KELT-9b orbiting its host star, KELT-9. It is the hottest gas giant planet discovered so far. Photo: NASA/JPL

Scientists have discovered the hottest known planet located 650 light years from Earth, which is warmer than most stars in the universe and sports a giant, glowing gas tail like a comet.

The Jupiter-like planet orbits a massive star KELT-9 every day and a half, researchers said.

With a day-side temperature peaking at 4,326 degree Celsius, the newly discovered exoplanet, designated KELT-9b, is hotter than most stars and only 926 degree Celsius cooler than our Sun.

Glowing gas tail

The ultraviolet radiation from the star it orbits is so brutal that the planet may be evaporating away under the intense glare, producing a glowing gas tail.

The gas giant 2.8 times more massive than Jupiter but only half as dense, because the extreme radiation from its host star has caused its atmosphere to puff up like a balloon.

Tidally locked

Since it is tidally locked to its star — as the moon is to Earth — the day side of the planet is perpetually bombarded by stellar radiation, and, as a result, the planet is so hot that molecules such as water, carbon dioxide and methane can not form there.

“It’s a planet by any of the typical definitions based on mass, but its atmosphere is almost certainly unlike any other planet we’ve ever seen just because of the temperature of its day side,” said Scott Gaudi, professor at the Ohio State University in the U.S. and lead author of the study published in the journal Nature .