Kepler-186f Orbiting A Distant Star.

The artist's concept depicts Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone. The size of Kepler-186f is known to be less than ten percent larger than Earth, but its mass, composition and density are not known. Kepler-186f orbits its star once every 130 days and receives one-third the energy that Earth does from the sun, placing it near the outer edge of the habitable zone. Kepler-186f resides in the Kepler-186 system about 500 light-years from Earth in the constellation Cygnus. The system is also home to four inner planets, seen lined up in orbit around a host star that is half the size and mass of the sun. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zones of other stars and signals a significant step closer to finding a world similar to Earth.