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]

    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.[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±4.7°.[3]

    Physical characteristics

    The planet is slightly less massive as Jupiter (0.919 ± 0.073 MJ) but its diameter is about 80% 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.[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]

    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.
    3. Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments, 2012, arXiv:1206.6105

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