13. Nearby Quasar
A quasar is an active supermassive black hole at the heart of a galaxy, emitting blinding jets of radiation. If one formed near the Milky Way, its intense energy could irradiate Earth, stripping away the atmosphere and making life impossible. Astronomers have observed these cosmic beacons in distant galaxies, as noted in NASA’s Chandra observations, and are grateful none are close by.