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Scientists have discovered a planet not much bigger than Earth that could be covered in oceans and has the right temperature to support life - and it is only 20.5 lightyears away.
By 2020, it should be possible for a telescope to take a close enough look at the discovery, which has yet to be named, to see if there is any sign of life.
The newly found planet is older than our solar system. It is revolving around the star known as Gliese 581, a "red dwarf" in the Libra constellation.
Its "year" lasts only 13 days because it is 14 times closer to its star than the Earth is to the sun.
But that is a good sign, because red dwarfs are less than half the size of the sun, and cooler.
In the zone where the new planet has been uncovered, surface temperatures would be between zero and 40C - just right for oceans to have formed and life to have begun.
It is the smallest planet yet discovered outside the solar system, with a radius about one and a half times that of Earth, giving it about twice the gravitational pull.
Any living creatures on it would need thick bones and sturdy legs, because they would be twice as heavy as on Earth.
Dr Malcolm Fridlund, of the European Space Agency, said: "This is a very important step on the road to finding Earth-like planets.
"The planets we've found so far outside the Solar System have all been different from our own Earth, and more like Jupiter or Neptune.
"If this is a rocky planet, it's very likely that it will have liquid water on its surface, which means there may also be life.
"There are caveats, one being that the environment around a red dwarf is very full of radiation.
"All red dwarfs have a lot of flare activity, but this doesn't necessarily exclude life."
The planet was found by Swiss, French and Portuguese astronomers using the European Southern Observatory's 3.6m telescope at La Silla in Chile.
They employed a method that looks for the "wobble" on a star caused by the gravity of a large object orbiting it. By measuring the wobble motion, astronomers can calculate a planet's orbit and mass.
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