An international team of astronomers has discovered the largest known exoplanet planet orbiting another star, BBC reported.
The new exoplanet is located in the constellation of Hercules and was discovered by a team working on the Transatlantic Exoplanet Survey (TrES), whose lead author is the Bulgarian Georgi Mandushev from the Lowell Observatory in Flagstaff.
The "transiting" planet - meaning one that passes in front of its parent star as seen from Earth - is about 70% larger than Jupiter.
The planet, called TrES-4, is a giant ball made of mostly hydrogen that is 20 times larger than Earth and circling a star 1,400 light years away. It is so big that it is baffling scientists and so light that it could theoretically float on water.
But the presumed "gas giant" has a much lower mass than Jupiter making it of extremely low density.
TrES-4 circles the star GSC02620-00648. Being only 7 million kilometres from its parent star, its temperature is about 1,327 degrees Celsius.TrES-4 was discovered using three telescopes, two in Arizona, in the US, and one in the Canary Islands.
Because of the relatively weak pull exerted by TrES-4 on its upper atmosphere, some of the atmosphere probably escapes in a curved comet-like tail.
"TrES-4 is the largest known exoplanet," said Mandushev.
Mandushev from the Lowell Observatory in Arizona is the lead author of the paper announcing the discovery in the Astrophysics Journal. He says TrES-4 appears to be almost puffed up.
"It's a very enigmatic planet, I would say, because it's so big and has such a low density," he said. "At this point, theoretical models of planets cannot explain this one."