spacetoday.net: Astronomers discovered largest known exoplanet

Posted: Wed, Aug 8, 2007, 7:42 AM ET (1142 GMT)
TrES-4 exoplanet illustration (Lowell Obs.)

Astronomers announced this week that they have discovered an extrasolar planet with the largest radius measured to date, making the planet's density unexpectedly low. The planet, designated TrES-4, closely orbits the star GSC02620-00648, 1,435 light-years away. The planet was discovered by detecting periodic decreases in the star's brightness as the planet transited the star's disk as seen from Earth. Those studies found that the planet has a radius 1.67 times that of Jupiter, the largest radius of any planet so far measured. Separate observations found that the planet's mass is only 0.84 times that of Jupiter, giving the planet a density of 0.22 grams per cubic centimeter, too low to be explained by current models of giant planets.