It takes more than four years for its light to reach us, but Proxima Centauri is one of our closest neighbors. The star orbits in the constellation of Centaurus, visible in the Southern Hemisphere, but itself is too faint to see with the naked eye. Proxima isn’t like our sun; it is smaller, dimmer, and cooler. These suns are prone to frequent flares of ultraviolet radiation, which can be bad news for planets orbiting too closely.
Some scientists think the bursts could strip away entire atmospheres and boil off oceans. But others think these conditions, as ferocious as they might be, could actually give rise to life.
That’s the hope of Lisa Kaltenegger and Jack O’Malley-James, who chat often about alien life over coffee at work—a typical office discussion for a pair of astronomers at the Carl Sagan Institute at Cornell University. Because Proxima has a planet, maybe even two. The known planet, Proxima Centauri b, is about the same size as Earth, and might be rocky like it, too. It resides in that magical slice of solar systems, the habitable zone, where conditions are not too cold or too hot for liquid water to burble on the surface.
Potential life on Proxima b—on any planets around other stars—probably won’t resemble the kind on our planet, Kaltenegger says, but earthly beings are the only blueprints we have. So the astronomers wondered, what happens here, when ultraviolet radiation from the sun smacks into lifeforms on Earth?