If extra-terrestrials do exist they must have a home. Horizon tells the story of the race to find out where in the Universe this might be. The answer, for scientists across the world, lies in the hunt for planets around distant stars. Stars which are trillions of miles away from our own solar system. But the history of the planet hunters is littered with failure. Centuries of searching had thrown up nothing. It was time for the new style planet hunters to step in. However, it is only in the last ten years that these scientists have had the technology to succeed. Even now looking for these distant planets is far from straightforward. The planets themselves are so faint that they cannot be seen, even by the most powerful telescopes ever built. Instead the astronomers must devise ingenious ways to search for clues to their presence. They examine stars just like our own Sun, across the galaxy, for any give-away characteristics that might indicate that they too have planets circling