Sometimes the corny wisdom that you can search far and wide for what’s right in front of you all along turns out to be true. For astronomers studying extrasolar planets—those around other stars, of which more than 3,500 are now known—the holy grail is an Earth-like world: small, rocky, and about the right distance from its star for liquid water to exist on the surface.
Now they have found one as near as could be. True, it is still a little more than four light years away—that’s around 25 trillion miles—but it is orbiting our Sun’s nearest neighbouring star, Proxima Centauri, in the constellation of Centaurus.
For one thing, the discovery drives home the message now abundantly clear from studies of extrasolar planets: terrestrial-like planets must be pretty commonplace throughout the cosmos. It’s now believed, on the basis of planet surveys to date, that around one in every five Sun-like stars has a planet of similar size and composition to Earth within their so-called habitable zone, where the temperature is right for liquid water to exist.
What’s more exciting is that it is not absurd to imagine sending a spacecraft (unmanned, of course) to Proxima Centauri to take a closer look. Indeed, earlier this year billionaire entrepreneur Yuri Milner announced a $100m project called Starshot to do just that. He believes a probe could potentially make the journey in just 20 years, although it would take any information sent back at the speed of light a further four and a bit years to reach us. The new discovery is sure to lend a huge boost to proposals of that kind.