The artist's concept depicts Kepler-186f , the first validated Earth-size planet to orbit a distant star in the habitable zone-a range of distance from a star where liquid water might pool on the planet's surface. The discovery from April 2014 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. 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. If you could stand on the surface of Kepler-186f, the brightness of its star at high noon would appear as bright as our sun is about an hour before sunset on Earth. 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. Image Credit: NAS...