'Dark stars' could be the seeds of supermassive black holes, scientists say

Scientists believe mysterious gravitational waves detected in 2023 could be the echoes of "dark stars" that served as the seeds for the first supermassive black holes. These low-frequency gravitational waves were detected using pulsars, which are rapidly spinning and highly magnetic neutron stars that emit beams of radiation. The pulsar timing array used to detect these waves measures tiny fluctuations in space and time caused by gravitational waves, or ripples in spacetime.

Although the origin of this particular low-frequency gravitational wave background has been a mystery, scientists hope it may provide insights into the early universe, specifically around 13 billion years ago. The researchers propose that these gravitational waves could help explain how supermassive black holes grew so rapidly before the universe was even a billion years old.

They suggest that these gravitational waves may be the result of the collapse and death of hypothetical "dark stars," which are thought to have collapsed and died in the early universe to create massive black hole seeds. Dark stars are theoretical primordial stars powered by self-annihilating dark matter within their cores. Unlike traditional stars that generate energy through nuclear fusion, dark stars remain cool and continue to accrete matter throughout their lives.

When dark stars reach a massive size (millions of times the mass of the sun), they collapse under their own gravity, creating black holes that merge and eventually form supermassive black holes. The team modeled the environment in which these black hole seeds would exist and merge, calculating merger rates and their influence on the gravitational wave background.

Their findings suggest that supermassive dark star remnants could contribute significantly to the gravitational wave background detected in 2023. However, determining if this theory is correct may require further improvements in pulsar timing array measurements and a better understanding of populations of black holes in the early universe.