TrES-4b


TrES-4b is an extrasolar planet, and one of the largest exoplanets ever found, after WASP-12b, WASP-17b, CT Chamaeleontis b and GQ Lupi b. It was discovered in 2006, and announced in 2007, by the Trans-Atlantic Exoplanet Survey, using the transit method. It is approximately away orbiting the star GSC 02620-00648, in the constellation Hercules.

Orbit

A 2008 study concluded that the GSC 06200-00648 system is a binary star system allowing even more accurate determination of stellar and planetary parameters.
TrES-4 orbits its primary star every 3.543 days and eclipses it when viewed from Earth.
The study in 2012, utilizing a Rossiter–McLaughlin effect, have determined the planetary orbit is probably aligned with the equatorial plane of the star, misalignment equal to 6.3°.

Physical characteristics

The planet is 0.919 times as massive as Jupiter but 1.799 times the diameter, the largest planet ever found at the time, giving it an average density of only about 0.333 grams per cubic centimetre, approximately the same as Saturn's moon Methone. This made TrES-4 both the largest known planet and the planet with the lowest known density at the time of its discovery.
TrES-4's orbital radius is 0.05091 AU, giving it a predicted surface temperature of about 1782 K. This by itself is not enough to explain the planet's low density, however. It is not currently known why TrES-4 is so large. The probable causes are the proximity to a parent star that is 3–4 times more luminous than the Sun as well as the internal heat within the planet.