A team of astronomers led by Carnegie’s Meredith MacGregor and Alycia Weinberger detected a massive stellar flare—an energetic explosion of radiation—from the closest star to our own Sun, Proxima Centauri, which occurred last March. This finding, published in Astrophysical Journal Letters, raises questions about the habitability of our Solar System’s nearest exoplanetary neighbor, Proxima b, which orbits Proxima Centauri.