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 1,400 light-years (430 pc) away orbiting the star GSC 02620-00648, in the constellation Hercules.[1]

TrES-4b
Size comparison of TrES-4 with Jupiter
Discovery
Discovered byMandushev et al.[1]
Discovery date2006-2007
Transit
Orbital characteristics
0.05091 ± 0.00071 AU (7,616,000 ± 106,000 km)[2]
Eccentricity0
3.553945 ± 0.000075 d
Inclination82.86 ± 0.33[2]
Semi-amplitude86.1
StarGSC 02620-00648 A[2]
Physical characteristics
Mean radius
1.799 ± 0.063[2] RJ
Mass0.919 ± 0.073[2] MJ
7.04 ± 1.12 m/s2 (23.1 ± 3.7 ft/s2)
0.718 ± 0.114 g
Temperature1782 ± 29[2]

    TrES-4 orbits its primary star every 3.543 days and eclipses it when viewed from Earth. The planet is 0.919 times as massive as Jupiter but 1.799 times the diameter, the largest planet ever found at the time (next to WASP-17b, found on 1 May 2009), 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.[2][1]

    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.[2][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]

    See also

    References
    1. Mandushev, Georgi; et al. (2007). "TrES-4: A Transiting Hot Jupiter of Very Low Density". The Astrophysical Journal Letters. 667: L195–L198. arXiv:0708.0834. Bibcode:2007ApJ...667L.195M. doi:10.1086/522115.
    2. Daemgen, S.; Hormuth, F.; Brandner, W.; Bergfors, C.; Janson, M.; Hippler, S.; Henning, T. (2009). "Binarity of transit host stars - Implications for planetary parameters" (PDF). Astronomy and Astrophysics. 498: 567–574. arXiv:0902.2179. Bibcode:2009A&A...498..567D. doi:10.1051/0004-6361/200810988.

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