A mysterious hum of gravitational waves that fills the cosmos may be the echo of "dark stars" that served as the seeds of the first supermassive black holes.
These low-frequency gravitational waves were detected back in 2023 using an array of cosmic lighthouses, or pulsars, in a so-called "pulsar timing array." Pulsars are neutron stars that spin rapidly and regularly while blasting out collimated beams of radiation from their poles that can be used to detect tiny fluctuations in space and time. Such fluctuations are caused by the gravitational waves, or ripples in spacetime.
For a long time, the source of this particular low-frequency gravitational wave background has been somewhat shrouded in mystery, but scientists have hoped that they may be encoded with the secrets of the universe as it was around 13 billion years ago. Indeed, the team behind this research believes this hum of spacetime ripples could help explain how supermassive black holes grew so rapidly before the universe was even a billion years old. They link this solution to hypothetical supermassive "dark stars" that may have collapsed and died in the early universe to birth massive black hole seeds, giving supermassive black hole growth a head start.
