Astronomers have discovered the smallest planet outside our solar system, and the first that is undoubtedly rocky like Earth. Measurements of unprecedented precision have shown that the planet, Kepler 10b,has a diameter 1.4 times that of Earth, and a mass 4.6 times higher.
However, because it orbits its host star so closely, the planet could not harbour life. The discovery has been hailed as "among the most profound in human history".
The result was announced at the 217th annual meeting of the American Astronomical Society in Seattle, US, by Nasa's Kepler team.
The Kepler space telescope, designed to look for the signs of far-flung planets, first spotted the planet 560 light-years away, alongside hundreds of other candidate planets. Kepler relies on the "transiting" technique, which looks for planets that pass between their host star and the Earth.
A tiny fraction of the star's light is blocked periodically, giving a hint that the star has a planet orbiting it. The radius of the planet correlates to exactly how much light is blocked when it passes.
Saturday, Mar 07th
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