Exoplanets - planets circling other stars - are being discovered by the dozen these days. Back in the dark times of the eighties and earlier some scientists doubted whether any other stars were accompanied by planets at all. Now you begin to wonder whether there's even such thing as a planetless star.

Since the discovery of the first one in 1988 the number of confirmed exoplanets now approaches 1,000 and given advances in observational technology can only grow at an ever increasing rate. As such the news of another discovery is hardly a matter for excitement any more.

Except the latest one.

They've found a planet in Alpha Centauri.

Alpha Centauri!

A system whose official stellar classification echoes down the annals of SF literature, film and TV like the name of an old friend. Everyone's heard of Alpha Centauri. It's not that remarkable a system in itself - just a bog standard double star each of which is approximately the same size and magnitude as our own sun, the pair orbited at a great distance by a dim red dwarf known as Proxima Centauri. From Earth it's only visible from the southern hemisphere, the brightest star in the constellation of Centaurus, a constellation first so named by the ancient Greeks.

It wasn't until the early nineteenth century that anyone realised there was anything special about it. That it was unique - the closest star to our own system. The next-door neighbours. From a planet circling Alpha Centauri the night sky would be more or less identical to our own with only two major differences. The constellation of Centaurus would be missing its brightest member. And the constellation of Cassiopeia would have gained an extra downstroke to her distinctive W shape, a new brightest star, our own sun.

Since the birth of Science Fiction Alpha Centauri has exerted a strong hold over the minds of writers. Bound to be our first port of call once we make the break out into the galaxy, one cannot help but wonder what we might find there.

In 1944 A E van Vogt suggested in his short story Far Centaurus that the first explorers to set off would find an Earth colony set up during their long journey by their faster than light traveling successors. The system continues to appear in written fiction on a regular basis throughout the twentieth century, with perhaps one of the most notable more recent examples being at the conclusion of William Gibson's trilogy of Neuromancer, Count Zero and Mona Lisa Overdrive when the newly sentient cyberspace matrix becomes aware of another example of its own kind in Alpha Centauri.

Visual media weren't slow to capitalise on the Nearest Star theme either. Alpha Centauri is the original destination of the crew of the Jupiter 2 before they become Lost in Space in the 1960s and meanwhile over in Star Trek the inventor of warp drive, Zefram Cochrane, spends some time living on Alpha Centauri before his mysterious disappearance. In Doctor Who it's home to the one eyed hermaphrodite hexapods who apparently played a mean game of table tennis. According to Douglas Adams it was inhabited by small furry creatures and was also home to the local branch of the hyperspace bypass planning department.

And most recently and perhaps most visibly, Alpha Centauri is the setting for James Cameron's 2009 blockbuster Avatar, where the world Pandora is a moon orbiting a gas giant in the self same system.

It's not surprising that it has such a powerful effect on our imaginations. The first interstellar voyage will be a step as important as Armstrong's, having broken free not only from our home planet but from our home system itself. And now we know there's definitely a planet there to land on. A destination. Hurry up and invent fast, efficient stardrives, people. We're getting impatient.

But it's important to remember that once out there we'll be on our own. Even from Alpha Centauri any cries for help would take four years to reach Earth.


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