The planet, which NASA calls Kepler-186f, is located in the constellation Cygnus, about 500 light-years from Earth. Kepler-186f orbits the star Kepler-186 once every 130 days and receives one-third of the energy from that star than Earth does from the sun, NASA said in a statement. The amount of energy Kepler-186f receives at noon is similar to what Earth receives an hour before sunset, which places the newly discovered planet at the outer edge of the habitable zone.

 NASA defines the habitable zone as “the range of distance from a star where liquid water might pool on the surface of an orbiting planet.” Being in the habitable zone, however, does not guarantee that life is possible, just that it could be.

"We know of just one planet where life exists -- Earth. When we search for life outside our solar system we focus on finding planets with characteristics that mimic that of Earth," Elisa Quintana, research scientist at the SETI Institute at NASA's Ames Research Center in Moffett Field, Calif., and lead author of the paper published in the journal Science, said in the NASA statement. "Finding a habitable zone planet comparable to Earth in size is a major step forward."