The black holes of the Milky Way rise from 2 to 10 which, while devouring gas and stardust, emit X-rays that bounce creating luminous echoes: the eight new specimens have been identified thanks to the 'Reverberation Machine', a new research tool automated capable of scanning satellite data for signals.
The echoes will be useful to map the environment around black holes and to better understand their evolution: this is indicated by the study published in The Astrophysical Journal by an international team led by the Massachusetts Institute of Technology (MIT), which in a side project has also translated the X-ray echoes into audible sounds.
"We see new reverberation signs in eight sources," says MIT astrophysicist Jingyi Wang.
"Black holes have a mass ranging from 5 to 15 times the mass of the Sun and are all inside binary systems with normal, low-mass, Sun-like stars."
While rare, these echoes can tell us a lot about the environment surrounding black holes.
Light can be analyzed (both from the initial explosion and from the echo) to measure the space between the black hole and the accretion disk dust, according to a principle similar to the echolocation used by bats to locate prey and move around in the darkness.
The echoes can also be used to study how the black hole's accretion disk and its corona (the region of very hot electrons between the inner edge of the accretion disk and the event horizon) change as the black hole 'feeds'. .
