The largest extrasolar planet or exoplanet has been discovered orbiting the star GSC 02620-00648, around 1,435 light years away. The planet, named TrES-4, after the Transatlantic Exoplanet Survey (TrES) is 1.7 times the size of the planet Jupiter. TrES-4 also has a lower mass than Jupiter and an extremely low density of 0.2 grams per cubic centimetre, which is less than a wine cork. Georgi Mandushev of the Lowell Observatory in Arizona said, "It's way lower than the density of water."

TrES-4 orbits its star at a distance of only 7 million km (4.5 million miles), meaning that the temperature of the planet is estimated at 1,327°C (approximately 1,600K or 2,300°F).

Mandushev went on to say, "Because of the planet's relatively weak pull on its upper atmosphere, some of the atmosphere probably escapes in a comet-like tail."

Due to the planet's size, current theories about superheated giant planets find it hard to explain why it is so large. Francis O'Donovan, a graduate student in astronomy at the California Institute of Technology which operates one of the TrES telescopes said, "We continue to be surprised by how relatively large these giant planets can be. But if we can explain the sizes of these bloated planets in their harsh environments, it may help us better understand our own Solar System planets and their formation."