An exoplanet is a planet which orbits a star outside our solar system. The discovery of Gliese 581c caused excitement because the exoplanet's surface is the right temperature to support alien life. In 1995 astronomers were amazed to see over 3,000 galaxies when they pointed the Hubble Space Telescope to a dark corner of Ursa Major. If an average galaxy contains 100 billion stars, and there is a one per cent chance of a star being orbited by an Earth-like habitable planet, that's a pretty good chance of extra-terrestrial life. 

Six real-life Star Wars worlds

The Stars Wars universe has been captivating audiences for decades, but astronomers are beginning to find alien worlds that bear an uncanny resemblance to the planets dreamt up by George Lucas.

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What if we find alien life?

Professor Stephen Hawking has launched a new, highly funded search for extraterrestrial intelligence, but what will happen if we actually do end up making first contact?