A planet discovered outside our solar system may be the right temperature to support life, scientists believe. An astronomy expert explains the significance of the discovery for Channel 4 News.
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The newly detected planet is three times the size of Earth and orbits a red dwarf star called Gliese 581.
Scientists at the University of California, Santa Cruz and the Carnegie Institution of Washington discovered the planet, which they described as "just right" for life - not too hot and not too cold. As a result of the description, some have dubbed it the "Goldilocks" planet, after the children's story.
The team found the planet using the Keck telescope in Hawaii, which has been observing the Gliese 581 star for 11 years. Their research was published in the Astrophysical Journal.
Steven Vogt of UC Santa Cruz said: "The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common."
The scientists estimate the temperature on the planet average from -24 to 10 degrees Fahrenheit (-31 to -12 degrees Centigrade). The planet orbits the star once every 37 days, the scientists estimated. Unlike Earth, it is locked into position facing its sun - so one side would be always hot, and one side always cold.
Hope for human life?
If the planet is rocky, like Earth, it could have similar gravity, and there could also be water on the planet - another key element for life, although the scientists have not detected any water at this stage.
However, any science fiction dreams of shifting part of the world's population to the new planet, called Gliese 581g, face some obstacles - not least that it is 20 light years away. A light year is the distance travelled by light in a year, totalling about 6 trillion miles.
But the scientists had some consolation for would-be space dwellers, and for those hoping a new planet could be an answer to climate change.
"There are now nearly 500 known extrasolar planets," the team said. "If the local stellar neighbourhood is a representative sample of the galaxy as a whole, our Milky Way could be teeming with potentially habitable planets."
Dr Robert Massey of the Royal Astronomical Society told Channel 4 News the discovery also improved the odds of other intelligent life existing in the Universe.
"If we run the clock forward by 10 years, we might find dozens or even hundreds of potentially habitable planets like this, with the new telescopes and technology. If this is the case, the odds of finding intelligent life vastly increase," he said.
"I think in 10 years we will have direct or indirect evidence for intelligent life," he added.
"This is a really big discovery and it won't be the last of its type, I think. It's one of the big challenges now for science, are we alone in the Universe? And things like this are part of the quest for the answer."