| TrES-4b | |
| Discoverer: | Mandushev et al |
| Discovered: | 2006–2007 |
| Discovery Method: | Transit |
| Apsis: | astron |
| Semimajor: | 0.05091± |
| Eccentricity: | 0 |
| Period: | 3.553945 ± 0.000075 d |
| Inclination: | 82.86 ± 0.33 |
| Semi-Amplitude: | 86.1 |
| Star: | GSC 02620-00648 A |
| Mean Radius: | 1.799 ± 0.063 |
| Mass: | 0.919 ± 0.073 |
| Surface Grav: | 0.718 ± 0.114 g |
| Single Temperature: | (1782K, equilibrium) |
TrES-4b is an extrasolar planet, and one of the largest exoplanets ever found. It was discovered in 2006, and announced in 2007, by the Trans-Atlantic Exoplanet Survey, using the transit method. It is approximately 1400ly away orbiting the star GSC 02620-00648, in the constellation Hercules.[1]
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.[2]
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°.
The planet is slightly less massive than 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 a third of a gram per cubic centimetre, approximately the same as Saturn's moon Methone. This made TrES-4b both the largest-known planet and the planet with the lowest-known density at the time of its discovery.[2] [1]
TrES-4b's orbital radius is 0.05091 AU, giving it a predicted surface temperature of about . This by itself is not enough to explain the planet's low density, however. It is not currently known why TrES-4b is so large. The probable causes are the proximity to a parent star that is three to four times more luminous than the Sun as well as the internal heat within the planet.[2] [1]