This week, Nasa shut down the Kepler space telescope, its eye in the sky. It had brought humanity one step closer to the dream of striking out into space by identifying over 2,600 exoplanets — planets outside our solar system. Many of them are in what is known as the “habitable zone”, in orbits where water can exist in liquid form. This is not a reliable livability index, of course. Mars is in the sun’s habitable zone, but as watchers of The Martian would appreciate, it’s a mighty hostile place.
Nevertheless, Kepler has demonstrated what the pioneering cosmologist Carl Sagan always preached, that there are habitable worlds out there, and possibly intelligent life that we could communicate with. The space telescope, which will now lie dormant in solar orbit for ever — unless it becomes a tourist attraction in about a century — had been faltering for some time. Two gyros which hold its eye steady on distant stars failed, and with remarkable ingenuity, engineers found a way to keep it locked on using the solar wind. But when the telescope lost power, there was no way to save it. Fortunately, the Transiting Exoplanet Survey Satellite (TESS), launched earlier this year, uses the same method as Kepler to identify distant planets, looking for blips in the intensity of stars when their planets pass across their face. More planets will be found.
But the most dramatic finding would be of intelligence out there, not from telescopes but from projects like the Search for Extraterrestrial Intelligence, which trawls the electromagnetic spectrum listening for chatter from distant stars. It could be just a ping or a whistle from light years away in space. We may not be able to read it, but we would know precisely what it means: “Here I am. Come and get me.”