ALIEN WORLDS IN FARAWAY GALAXIES: EXTRAGALACTIC PLANETS

The search for alien worlds continues, with surprising consequences

- Colin Stuart

We should count ourselves lucky. For thousands of years humans have gazed up at the night sky, wondering whether or not we are alone. We are among the first generations to know for sure that our Solar System is just one of many strung out across the vast cosmos. Our discovery of around 4,000 alien worlds dancing around distant stars – known as exoplanets – over the last three decades has quite rightly been lauded. It’s a wonderful achievement that helps put us in our astronomical place. The haul has thrown up a zoo of exciting and enchanting worlds, from those that dance around two suns to planets with diamond rain, bubbling metal lava and possibly even liquid water.

Despite the accolades, these discoveries are rarely put into their true context. It is easy to forget just how much of the universe’s real estate remains unexplored. All of the confirmed planets found to date reside in our own Milky Way galaxy, and in our tiny corner of it to boot. There are around 2 trillion other galaxies in the observable universe. To see how much we’ve poked around in so far, imagine that this hoard of galaxies is represented by the total land area of the Earth. On that scale, our Milky Way accounts for the space taken up by the average UK bungalow. The area that includes the thousands of exoplanets we’ve found so far is smaller than a sock drawer in the spare bedroom.