what is kepler 186f

Kepler-186f is an exoplanet that orbits within the habitable zone of the red dwarf star Kepler-186, located about 580 light-years from Earth in the constellation of Cygnus. It is the first validated Earth-sized planet to orbit a distant star in the habitable zone, where liquid water might pool on the planets surface. Kepler-186f orbits its star at a distance of about 0.43 AU (64,000,000 km; 40,000,000 mi) with an orbital period of roughly 130 days, and has a mass and radius around 1.44 and 1.17 times that of Earth, respectively. It is one of the more promising candidates for habitability and was the first planet with a radius similar to Earths to be discovered in the habitable zone of another star. Kepler-186f is estimated to receive about 5% of the Suns luminosity, and the habitable zone for this system is estimated conservatively to extend over distances receiving from 88% to 25% of Earths illumination. The planet is located in the Kepler-186 system, which is also home to four inner planets, but Kepler-186f is the only one in the habitable zone.