is also hotter than the Sun, although it is approximately three quarters of a billion years younger and is slightly less metal-rich. Characteristics Kepler-8b has about 60.3% as massive as Jupiter, but being 41.9% wider, it has a very sparse density of about . Based on its size and the distance from its star, Kepler-8b is a Hot Jupiter planet, orbiting Kepler-8 from a distance of every . To compare, planet Mercury orbits the Sun at an average distance of every . With an equilibrium temperature of , Kepler-8b was the hottest of the five planets announced during the conference stating its discovery. Kepler-8b has an eccentricity of nearly 0, which means that its orbit is very circular. As Kepler-8b orbits its star, it demonstrates the Rossiter–McLaughlin effect, in which the host star's spectrum becomes red- and, later, blueshifted, as a body transits it. The identification of this effect established Kepler-8b as orbiting in a prograde motion (as opposed to retrograde motion, in which a planet orbits in a direction opposite of its star's rotation). The study in 2012, have determined the planetary orbit is probably well-aligned with the equatorial plane of the star, deviating by 5°. The planet is likely to be tidally locked to the parent star. In 2015, the planetary nightside temperature was estimated to be equal to . See also Kepler-4b Kepler-5b Kepler-6b Kepler-7b Kepler-9b Kepler-10b References External links Exoplanets discovered in 2010 Hot Jupiters Giant planets Transiting exoplanets Lyra (constellation) 8b