You won’t hear them say it, but some of the world’s most acclaimed astronomers have been frustrated for the better part of two decades. In that time they and their colleagues have found thousands of exoplanets—planets orbiting stars other than our sun—and have statistically surmised that hundreds of billions more await discovery in our galaxy alone. Swat any star hard enough with state-of-the-art instrumentation, it seems, and it will eventually spill out new worlds like candy pouring from a split piñata. The planet hunters have already unwrapped some of their haul, using telescopes to closely study and even image a small number of unappetizingly uninhabitable gas-giant worlds. Yet so far they have failed to sample the sweetest, most tantalizing pieces to fall in their laps—a handful of potentially Earth-like worlds that could harbor life.
Not that they haven’t tried. Even if only composed of a single noisy pixel, a picture snapped of a promising planet around another star would go a long way toward telling whether that world is really habitable, or even potentially inhabited. It could be the first glimmer of the greatest discovery in human history—proof that we are not cosmically alone. Alas, today’s best telescopes have fallen short. Their large and sophisticated optics are still too small and simplistic to distinguish the faint form of a rocky world whirling amid the glare of a star. Something bigger and bolder seems to be required. To find another Earth, the thinking goes, one must first build a planet-imaging telescope of such size, sophistication and cost that it becomes too big to fail. To build such a telescope, however, one must first find another Earth it could conceivably study. If “show us the money” is the planet hunters’ plea, “show us the planet” is the surefire policymakers’ reply. This catch-22 has left astronomers planning how they’ll image and study Earth-like planets in a future that seems destined to never arrive.
No longer. Due to a single discovery announced last month, that future may play out over the next several years with astronomers using existing and under-construction telescopes on the ground and in space, rather than in fanciful far-future observatories. The catalyst for this epochal transition is Proxima b, a newfound small planet orbiting Proxima Centauri, which at just over four light-years away is the star nearest to our solar system. “Proxima b has drawn a chalk line high up on the wall, and we are all now jumping to reach it,” says Matthew Kenworthy, an astronomer who works on new planet-imaging techniques at Leiden Observatory in the Netherlands. “E-mails are flying back and forth, people are dusting off methods they came up with years ago for seeing a rocky planet that were shelved for lack of finding any nearby. You can practically hear the frenzied brain waves passing through the air. It’s energizing for everyone to know there’s this beautiful, very exciting target right next door.”
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