HAT-P-6b
HAT-P-6b is a transiting extrasolar planet discovered by Noyes et al. on October 15, 2007. It is located approximately 910 light-years away in the constellation of Andromeda, orbiting the star HAT-P-6. This hot Jupiter planet orbits with a semi-major axis of about 7.832 gigameters, and takes 92 hours, 28 minutes, 17 seconds and 9 deciseconds to orbit the star. 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..
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. The Nachtwacht is a world-famous painting by Dutch grand master Rembrandt.
The sky projected angle between stellar and orbital axis is roughly 166°, making it one of the few planets that is in a retrogade orbit around its parent star. 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.
