'Exoplanet' could be habitable
A planet 20 light years away is the first outside the Solar System to be officially declared habitable by scientists.
The "exoplanet" Gliese 581d has conditions that could support Earth-like life, including possible watery oceans and rainfall.
Yet any future space voyagers landing there would find themselves in truly alien surroundings.
The sky is likely to be murky red, not blue, and gravity is twice what is on Earth, doubling the weight of anyone standing on the surface.
In addition, the planet's carbon dioxide-rich atmosphere would almost certainly not be breathable by humans.
Scientists were surprised by the discovery because Gliese 581d was previously ruled out as a habitable planet candidate.
But a new computer model capable of simulating extraterrestrial climates has shown the previous assumption to be wrong, and confirmed that Gliese 581d really could harbour life.
Scientists believe the findings could pave the way to more discoveries of potential havens for life among the stars, including some that are strange and unexpected.
Dr Robin Wordsworth, a member of the French team from the Institut Pierre Simon Laplace in Paris, said: "This discovery is important because it's the first time climate modellers have proved that the planet is potentially habitable, and all observers agree that the exoplanet exists.
"If you look at the history of the search for habitable planets, there's been at least two instances so far when scientists have announced that a habitable world has been discovered, only to have the claim contradicted later, either by climate experts or by other observers.