It's the perfect place for a quiet-living sort, a get-away-from-it-all location free from supermarkets, strip malls and litter. Views unimpaired by phone masts, tall buildings or, indeed, any human development, are guaranteed. Busy roads aren't a problem. Ditto noisy neighbours - in fact, you won't hear a peep out of them for at least a billion years. If you're trying to shed the pounds, though, this may not be the place for you, as your weight will shoot up the moment you set foot here.

Exoplanet Gliese 581C may not be admitting visitors yet but, as scientists announced this week, it is the most earth-like planet to be found outside our solar system to date. Crucially, its temperature is such that any water there could be in liquid form, raising the tantalising possibility that, like earth, it might support life. It's 20.5 light years away in the constellation Libra "so we won't be going there any time soon", according to those who know. Nevertheless, it's worth bearing in mind in case of future earthly catastrophe or, more optimistically, for the moment we develop new kinds of propulsion technology allowing us to go in search of ET.

Although it's 14 times closer to its sun than we are to ours, Gliese 581C's sun is smaller and cooler. So this sister earth, which completes its orbit in 13 days, is in what's known as the "Goldilocks zone" where temperatures are "not too hot" and "not too cold" but just right to create conditions for life support. Its average temperature is calculated as being between zero and 40 degrees celsius.

So what does Gliese 581C look like? That we don't yet know for sure. It was discovered using a 3.6m telescope at the European Southern Observatory (Eso) facility at La Silla in the Atacama Desert, Chile, but much of the information scientists have about it has been derived from models. It has a radius 1.5 times that of earth and a total mass five times the size. Modelling indicates that it's either rocky or covered in oceans. What life it might harbour is a mystery.

Still, there's no harm in speculating and all sorts of eminent boffins have been doing just that. The most likely scenario is that Gliese 581C harbours bacteria, according to Martin Griffiths of the Centre for Astronomy and Science Education at Glamorgan University; for three billion years of evolution on earth, microbiological life forms were all there was. Others say there's no point in trying to guess, as the evolutionary pathway of life on another planet might have produced something completely different to life on earth.

For the time being, we just don't know what's there. But we may not have to wait until Virgin Galactic works out how to travel at warp speed to find out. Astronomers can search for clues that life exists in other parts of the galaxy by sending telescopes into space looking for light "signatures" that could be linked to biological processes. These include traces of gases such as methane or tell-tale signs of chlorophyll.

If humans ever did go to Gliese 581C, though, they'd have to contend with gravity which was 1.5 times that on earth, which would be a bit like having magnets stuck to the soles of your shoes. If we stayed long enough, we'd probably evolve into squat little people with sturdy legs.

All that lies some way in the future. But the Gliese 581C discovery is hugely significant. More than 200 other exoplanets - planets orbiting stars other than our own sun - have been found but most are gas giants such as Jupiter (which is about 90% hydrogen and 10% helium). Gliese 581C is the one many scientists - and sci-fi fans - have been waiting for.