WASHINGTON (dpa-AFX) - In the search for Earth-like planets by NASA's Kepler mission, another important milestone has been reached following the discovery of two Earth-size planets called Kepler-20e and Kepler-20f.
The two planets are the first Earth-size planets to be discovered orbiting a sun-like star called Kepler-20, outside our solar system. Kepler-20 is about 1,000 light-years away from the Earth in the constellation Lyra.
The new planets - Kepler-20e and Kepler-20f, are thought to be rocky and are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet's surface, NASA noted.
Kepler-20e measures 0.87 times the radius of Earth, has a surface temperature of more than 1,400 degrees Fahrenheit and orbits its parent star every 6.1 days. Kepler-20f is a bit larger than Earth, measuring 1.03 times its radius, has a surface temperature of 800 degrees Fahrenheit and orbits its parent star every 19.6 days. The short orbital periods obviously mean very hot, inhospitable worlds.
Apart from the two newly discovered planets, Kepler-20 has three other planets, namely, Kepler-20b, Kepler-20c and Kepler-20d.
Earlier in the month, Kepler mission confirmed its first planet - Kepler-22b, in the 'habitable zone,' the region where liquid water could exist on a planet's surface. Kepler-22b, which is located 600 light-years away, is larger than Earth, has a surface temperature around 72 degrees and orbits its star in 290 days.
The Kepler Mission is specifically designed to discover hundreds of Earth-size and smaller planets in or near the habitable zone. The mission was launched in March 2009.
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