| By Joe Campbell BBC News Magazine |
Astronomers think they may have struck gold in their search for a planet beyond ours that could sustain life, but just what kind of neighbours should we expect if they come calling?
Whether they are little green men or the grey, bug-eyed aliens beloved of those who live in hope that we are not alone, the one message all the scientists can agree on is do not hold your breath waiting for their knock at the door.
At a distance of more than 20 light years from Earth, Gliese 581c is not exactly on the doorstep. 
So far we know it is about three times the diameter of the third rock from our sun and just like our home, it lies in the so called "Goldilocks Zone", that relatively narrow band of space around a star that is neither too hot nor too cold for us to hope that life may have evolved there
Ask the experts what life may be like and that is where the disagreements start to emerge.
"The planet may be habitable, but I wouldn't expect to see any intelligent life forms, " says Martin Griffiths, senior lecturer at the Centre for Astronomy and Science Education at the University of Glamorgan.
"We might see bacteria or something like that. You have to consider that for three billion years of our own evolution, the entire continuum of life here was microbiological, so I'd expect to find something like that."
Down the years most of our images of alien life have come not from the world of science but from the field of entertainment.
Scientific speculation has led to the appearance of everything from airborne jellyfish drifting through alien skies to heavily armoured crab like creatures scuttling across deserts warmed by distant suns, on television and cinema screens.
We're limited by our imaginations in a way life on alien worlds certainly wouldn't be 
Hollywood and home-grown depictions of extra-terrestrials maybe be dismissed by the world of science, but Dr Jack Cohen, author of the book, What Does a Martian Look Like?' says fellow academics are probably no closer to the truth.
"We're limited by our imaginations in a way life on alien worlds certainly wouldn't be," he says.
"If you ran the Earth again as an experiment, you wouldn't get humans. What a planet is like doesn't determine what the evolution will be like."
What scientific speculation there has been, he compared to the early fossil hunters who devised entire creatures from a few scraps of a skeleton - often producing creatures that seem almost comic in the eyes of today's dinosaur experts.
'Expect the unexpected'
Dr Cohen says life on other worlds might be so completely different to anything humans have knowledge of, it might not even be recognisable to us as life.
Professor Mark Brake, who helped set up the first course in Britain into the study of astrobiology says we are no closer to finding out what life of other worlds might be like than when the Greek satirist Lucian first speculated on the idea around 100AD.
"My first thought on all this is a line from The Hitch Hiker's Guide to the Galaxy that you should expect the unexpected," he says.
"Whatever life out there looks like, it's more likely than not it won't be anything like us at all."
Any life forms would have evolved to deal with the planet's gravity which would be around one-and-a-half times that of the Earth's, because of its greater mass.
Does that mean any extra-terrestrial visitors from the newly found planet would be able to leap tall buildings here on earth like Superman, that other product of a high gravity alien world?
"Going to visit them would certainly make us feel heavier and it would take more effort just walking around," says Martin Griffiths.
"It wouldn't have a substantial effect on us in the short-term, but if we stayed we'd probably evolve ourselves into people who were short and squat."
Voyage of discovery
The only way we will ever know for certain whether life exists on this new super-size Earth will be to go there, and with current space exploration technology that won't be happening any time soon.
"I just wish I was alive to see that day," says mathematician and part-time sci-fi writer, Professor Ian Stewart of the University of Warwick.
But like many interested in the relatively new science of astrobiology, he is travelling hopefully on the still Earth-bound voyage of discovery.
"A few years ago we couldn't find planets out there, then the ones we could see were too big to support life and now we've found one that's almost Earth size so at least I've lived to see that."
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