TrES-4b

TrES-4b is an extrasolar planet, and one of the largest exoplanets ever found, after WASP-12b, WASP-17b, CT Chamaeleontis b (though the latter may be a brown dwarf) 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 (among others) 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 slightly less massive as Jupiter (0.919 ± 0.073 ) but its diameter is 79.9% larger; it was considered the largest planet ever found at the time, giving it an average density of only about 1/3 gram 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.