NASA and Kepler telescope researchers have just announced that they've discovered an Earth-size planet circling a dwarf star at a distance that would allow that planet to support liquid water. The announcement was made in a live press conference attended by a panel of scientists that included Douglas Hudgins of NASA's Astrophysics Division, Elisa Quintana of the SETI Institute at NASA's Ames Research Center, Tom Barclay of Bay Area Environmental Research Institute at Ames, and Victoria Meadows of the University of Washington and the NASA Astrobiology Institute at Ames.
The new planet, Kepler-186f, is part of a five-planet planet system that orbits a star named Kepler-186, which is cooler and about half the size and mass of our sun. The newfound system is located about 500 light-years from Earth in the constellation Cygnus. Kepler-186f is the outermost planet and the only one circling its star at the right distance to have liquid water on its surface. Since liquid water is a key ingredient for life to exist, scientists call this sweet spot the "habitable zone."
On planets that are too close to their star, liquid water boils away. Those that are too far don't get enough energy from their star to support a climate and atmosphere similar to Earth. The planets were discovered using the Kepler spacecraft, launched in 2009, to look for Earth-size planets near stars like our sun. Kepler has found dozens of exoplanets in the habitable zone, but most of these are gas giants. Kepler-186f is the first confirmed plants that's roughly the size of Earth and potentially has an Earth-like atmosphere with water at its surface.