and Kepler-8b, were announced at the 215th meeting of the American Astronomical Society of January 4, 2010. Host star Kepler-5 is a subgiant in the Cygnus constellation that is expected to soon deplete its hydrogen stores in the core and begin fusing hydrogen in the shell region surrounding the core. The star is 1.374 times the mass of the Sun (another model suggests that Kepler-5 as a mass of 1.21 times that of the Sun), although it is more diffuse at 1.793 times the Sun's radius. The star's metallicity is measured to be at [Fe/H] = 0.04, which means that Kepler-5 has 1.10 times the levels of iron as the Sun does. The star's apparent magnitude is 13.4, meaning that it cannot be seen with the unaided eye. Characteristics Kepler-5b is a Hot Jupiter with a mass that is 2.114 times that of Jupiter and a radius of 1.431 times Jupiter's radius. This also means that Kepler-5b is not very dense. The planet's measured density is 0.894 grams/cm3, less than that of pure water and comparable only to the density of Saturn, which is approximately 0.69 grams/cm3. The planet has an equilibrium temperature of 1868 K, making it fifteen times hotter than Jupiter. Kepler-5b orbits its host star every 3.5485 days at a mean distance of 0.05064 AU. In addition, with an orbital inclination of 86.3º, Kepler-5b orbits Kepler-5 almost edge-on with respect to Earth. In comparison, planet Mercury orbits the Sun at a distance of 0.387 AU every 87.97 days. The planet is likely to be tidally locked to the parent star. In 2015, the planetary nightside temperature was estimated to be equal to 2169 K. References External links Discovery of the Transiting Planet Kepler-5b Exoplanets discovered in 2010 Hot Jupiters Giant planets Transiting exoplanets Cygnus (constellation) 5b