NASA's Kepler Space Telescope finds Earth twin

NASA's Kepler Space Telescope has discovered what is supposed to be the first planet of Earth's size that reportedly orbits a star in the "habitable zone".

Paul Hertz, NASA's Astrophysics Division director said that the discovery of Kepler-186f was a momentous step toward finding worlds like planet Earth.

"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," Hertz said.

Elisa Quintana, research scientist at the SETI Institute at NASA's Ames Research Center said, "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".

Whilst explaining the "habitable zone"Thomas Barclay, research scientist at the Bay Area Environmental Research Institute at Ames said that, "Being in the habitable zone does not mean we know this planet is habitable. The temperature on the planet is strongly dependent on what kind of atmosphere the planet has".

The four companion planets, Kepler-186b, Kepler-186c, Kepler-186d, and Kepler-186e, move quickly around their sun every four, seven, 13, and 22 days, respectively, making them too hot for life.