A rocky planet, whose mass is three times that of Earth's, could be the first ever to be found outside our solar system with the potential to support human life. Lying in the 'Goldilocks Zone' of the Milky Way, twenty light years away, the planet is said to have gravity similar to Earth and could well be capable of supporting life. The 'Goldilocks Zone' is a region in space where surface temperatures are neither too hot nor too cold for liquid water to form oceans, lakes and rivers. 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 number of systems with potentially habitable planets is probably in the order of 10 or 20 per cent, and when you multiply that by the hundreds of billions of stars in the Milky Way, that's a large number. There could be tens of billions of these systems in our galaxy.