Astronomers hear a mysterious cosmic hum linked to strange dark stars from 13 billion years ago

{}Astronomers may have found a new way to investigate the Universe's first supermassive black holes. A faint gravitational-wave hum detected through pulsars could contain clues about ancient objects. Hypothetical Dark Stars, powered partly by dark matter, could have left black-hole descendants. These ancient black-hole seeds could grow and merge, producing part of the gravitational-wave background.