Kepler-47 c orbits two suns. Kepler-47 is a pair of stars about 3,400 light-years away, a Sun-like star and a companion about a third its size, that circle each other every 7.45 days, and Kepler-47 c circles both of them every 303 days. By 2019, Kepler-47 was still the only system known with more than one planet orbiting a pair of stars that cross in front of each other.
A team led by Jerome Orosz found it with NASA's Kepler space telescope, which caught the planets crossing in front of the stars. Orosz's team noted that, although the planet is not Earth-like, it lies within the classical habitable zone of the pair, the range of distances where liquid water could exist on a planet's surface. Kepler-47 c is about 4.7 times Earth's width.
In 2019 the same group found a third planet, Kepler-47 d, between the other two, with an orbit of 187 days. Its gravity let them pin down the planets' masses much better than before. Kepler-47 c came out at only about 2 to 5 Earth masses, which, for its size, means a density of less than about a quarter of water's, so it is likely mostly a puffy envelope of gas rather than a planet with a solid surface. The team found the three orbits nearly circular and lying almost in one plane, which suggests the planets drifted gently into place rather than being scattered.