Artist’s conception of 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 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 is an exoplanet orbiting the red dwarf Kepler-186, about 500 light-years (171 parsecs, or nearly 5.298×1015 km) from the Earth. NASA’s Kepler spacecraft detected it using the transit method, along with four additional planets orbiting much closer to the star (all modestly larger than Earth). Analysis of three years of data was required to find its signal. The results were presented initially at a conference on March 19, 2014 and some details were reported in the media at the time. The public announcement was on 17 April 2014, followed by publication in Science.