A planet about 2 and a half times the size of the Earth has been found outside our solar system firmly placed in a habitable orbit around it's own sun. The planet, discovered by Nasa's Keppler spacecraft and dubbed Keppler 22b, might have an average temperature of 72 degrees making it possible for water to exist. Kepler-22b is about 600 light years from Earth, and orbits slightly closer to its sun than we do to ours. So far, Kepler has confirmed the existence of 28 planets outside the solar system, and found evidence of more than 2,300 more.