All eyes on Proxima Centauri b
An Earth-sized planet next door: that was the startling announcement last August. Astronomers had found an exoplanet orbiting the sun’s closest stellar neighbor, a cool red dwarf star called Proxima Centauri (1). Even better, the nearby world orbited within its parent star’s habitable zone, meaning liquid water could exist on the planet’s surface, which raised the prospects for its harboring life.



Proxima b, shown here in an artist’s conception orbiting the red dwarf star Proxima Centauri, may prove to be a test case for how astronomers conduct initial inspections of potentially habitable planets. Original image courtesy of ESO/M. Kornmesser; retouched version courtesy of Wikimedia Commons/Karl 432.



But aside from its mass—at least 1.3 times that of Earth’s—and the length of its year—a zippy 11 days—little was known about the new exoplanet, called Proxima Centauri b. Almost immediately, a rush of papers appeared, presenting ways to estimate Proxima b’s temperature, atmospheric composition and thickness, and even whether a worldwide ocean spans its surface. The proposed methods are extraordinarily tricky, pushing the boundary of what’s possible.

“This planet is so good, so optimum, and so close to us, that using state-of-the-art technology we [can] demonstrate that it’s not science fiction to do these observations,” says astronomer Christophe Lovis of the University of Geneva in Switzerland. With two recently discovered systems garnering ample headlines—the potentially habitable planets near the star TRAPPIST-1 and a super-Earth orbiting the red dwarf LHS 1140—Proxima b offers a test case for how astronomers might take the first steps toward closer inspection of planets that seem to be prime candidates for life (2, 3).

In the future, enormous ground-based telescopes and specially designed space-based ones will allow astronomers to image exoplanets like Proxima b directly, providing unparalleled information about them. And with the world a mere 4.25 …