Astronomers, using Nasa’s Kepler Space Telescope, have discovered the first Earth-size planet orbiting a star in the “habitable zone”. Kepler-186f.
“The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth,” said Paul Hertz, NASA’s Astrophysics Division director at the agency’s headquarters in Washington.
“Future NASA missions, like the Transiting Exoplanet Survey Satellite and the James Webb Space Telescope, will discover the nearest rocky exoplanets and determine their composition and atmospheric conditions, continuing humankind’s quest to find truly Earth-like worlds.”
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 companion planets, which orbit a star half the size and mass of our sun. The star is classified as an M dwarf, or red dwarf, a class of stars that makes up 70 percent of the stars in the Milky Way galaxy.
Kepler-186f orbits its star once every 130-days and receives one-third the energy from its star that Earth gets from the sun, placing it nearer the outer edge of the habitable zone.
On the surface, the brightness of its star at high noon is only as bright as our sun appears to us about an hour before sunset.