Coordinates: Sky map 23h 39m 05.8061s, +42° 27′ 57.513″
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HAT-P-6b / Nachtwacht
Size comparison of HAT-P-6b with Jupiter.
Discovered byNoyes et al.
Discovery dateOctober 15, 2007
Orbital characteristics
3.852985±0.000005[2] d
Inclination166±10 °[3]
Physical characteristics
Mean radius
1.33 ± 0.06 RJ[2]
[1] MJ
Mean density
583 kg/m3 (983 lb/cu yd)[1]

HAT-P-6b is a transiting extrasolar planet discovered by Noyes et al. on October 15, 2007.[2] It is located approximately 910 light-years away[4] in the constellation of Andromeda, orbiting the star HAT-P-6. This hot Jupiter planet orbits with a semi-major axis of about 0.05 AU, and takes 92 hours, 28 minutes, 17 seconds to orbit the star.[2] It has true mass of 5.7% greater than Jupiter and a radius 33% greater than Jupiter, corresponding to a density of 0.583 g/cm3, which is less than water.[1]

The planet HAT-P-6b is named Nachtwacht. The name was selected in the NameExoWorlds campaign by the Netherlands, during the 100th anniversary of the IAU, after Rembrandt's painting The Night Watch.[5][6]

The sky projected angle between stellar and orbital axis is roughly 166°, making it one of the few planets that is in a retrograde orbit around its parent star.[3] Observations made by Spitzer Space Telescope shows that the planet atmosphere has a weak temperature inversion, or no inversion at all, depending on how strong is the stellar chromospheric activity.[7]

Artist's impression of Hat-P-6b orbiting its host star with an aurora on its south pole.


  1. ^ a b c d e Bonomo, A. S.; et al. (2017). "The GAPS Programme with HARPS-N at TNG . XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets". Astronomy and Astrophysics. 602. A107. arXiv:1704.00373. Bibcode:2017A&A...602A.107B. doi:10.1051/0004-6361/201629882. S2CID 118923163.
  2. ^ a b c d Noyes, R. W.; et al. (2008). "HAT-P-6b: A Hot Jupiter Transiting a Bright F Star". The Astrophysical Journal Letters. 673 (1): L79–L82. arXiv:0710.2894. Bibcode:2008ApJ...673L..79N. doi:10.1086/527358. S2CID 2301387.
  3. ^ a b Hébrard, Guillaume; Ehrenreich, David; Bouchy, François; Delfosse, Xavier; Moutou, Claire; Arnold, Luc; Boisse, Isabelle; Bonfils, Xavier; Díaz, Rodrigo F.; Eggenberger, Anne; Forveille, Thierry; Lagrange, Anne-Marie; Lovis, Christophe; Pepe, Francesco; Perrier, Christian; Queloz, Didier; Santerne, Alexandre; Santos, Nuno C.; Ségransan, Damien; Udry, Stéphane; Vidal-Madjar, Alfred (2011). "The retrograde orbit of the HAT-P-6b exoplanet". Astronomy and Astrophysics. 527: L11. arXiv:1101.5009. Bibcode:2011A&A...527L..11H. doi:10.1051/0004-6361/201016331. S2CID 56130884.
  4. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  5. ^ "Approved names". NameExoworlds. Retrieved 2020-01-02.
  6. ^ "International Astronomical Union | IAU". www.iau.org. Retrieved 2020-01-02.
  7. ^ Todorov, Kamen O.; Deming, Drake; Knutson, Heather A.; Burrows, Adam; Sada, Pedro V.; Cowan, Nicolas B.; Agol, Eric; Desert, Jean-Michel; Fortney, Jonathan J.; Charbonneau, David; Laughlin, Gregory; Langton, Jonathan; Showman, Adam P.; Lewis, Nikole K.; Gratton, R.; Maggio, A.; Micela, G.; Molinari, E.; Pagano, I.; Piotto, G.; Poretti, E.; Smareglia, R.; Affer, L.; Biazzo, K.; Bignamini, A.; Esposito, M.; Giacobbe, P.; Hébrard, G.; Malavolta, L.; et al. (2012). "Warm Spitzer Observations of Three Hot Exoplanets: XO-4b, HAT-P-6b, and HAT-P-8b". The Astrophysical Journal. 746 (1): 111. arXiv:1111.5858. Bibcode:2012ApJ...746..111T. doi:10.1088/0004-637X/746/1/111. S2CID 119200344.

External links[edit]

Media related to HAT-P-6 b at Wikimedia Commons