A team of astrophysicists, led by scholars from the Institute for Advanced Study, has developed an innovative technique to search for black hole light echoes. Their novel method, which will make it easier for the mass and the spin of black holes to be measured, represents a major step forward, since it operates independently of many of the other ways in which scientists have probed these parameters in the past.
The research, published today in The Astrophysical Journal Letters, introduces a method that could provide direct evidence of photons circling black holes due to an effect known as “gravitational lensing.”
Gravitational lensing occurs when light passes near a black hole and its path is bent by the black hole’s strong gravitational field. The effect allows the light to take multiple paths from a source to an observer on Earth: some light rays might follow a direct route while others could loop around the black hole once—or multiple times—before reaching us. This means that light from the same source can arrive at different times, resulting in an “echo.”
“That light circles around black holes, causing echoes, has been theorized for years, but such echoes have not yet been measured,” says the study's lead author, George N. Wong , Frank and Peggy Taplin Member in the Institute’s School of Natural Sciences and Associate Research Scholar at the Princeton Gravity Initiative at Princeton University. “Our method offers a blueprint for making these measurements, which could potentially revolutionize our understanding of black hole physics.”