A SMALL planet about seven times as massive as the Earth has been spotted circling a nearby star. It is the most Earth-like world yet to be discovered.
鈥淔or the first time, we are beginning to find our planetary kin among the stars,鈥� says Geoff Marcy of the University of California at Berkeley, whose team announced the discovery of the planet at a news conference in Arlington, Virginia, on Monday.
Over the past decade, astronomers have discovered around 150 extrasolar planets circling ordinary stars like the sun. The vast majority of the planets have been gas giants larger than Jupiter, with even the smallest still 14 times the mass of Earth. That makes the new planet by far the smallest discovered. It orbits a red dwarf called Gliese 876, just 15 light years away in the constellation Aquarius.
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It might turn out to be a rocky planet, like Earth, but in other ways does not bear much resemblance to our own. A year on the planet lasts just 1.94 Earth days, and it orbits only 3.2 million kilometres away from its star 鈥� 2 per cent of the Earth-sun distance 鈥� so its surface temperature must be higher than 200 掳C. 鈥淏ecause the planet is in a two-day orbit, heated to oven-like temperatures, we do not expect life,鈥� says Marcy鈥檚 colleague Paul Butler of the Carnegie Institution of Washington DC.
Astronomers expect to find even smaller planets soon. And space-based missions such as NASA鈥檚 Terrestrial Planet Finder, which is due for launch around 2014, should be able to spot habitable Earth-like planets in droves.
