December 1, 2023

Astronomers have found evidence for five dual supermassive black holes in the centers of galaxies, each containing millions of times the mass of the Sun. These black hole couples formed when two galaxies collided and merged with each other, forcing their supermassive black holes close together.

Before this study fewer than ten confirmed pairs of growing black holes were known from X-ray studies, based mostly on chance detections. To carry out a systematic search, a team of researchers had to carefully sift through data from telescopes that detect different wavelengths of light.

After first identified promising candidates in optical and infrared data, the researchers then used data from NASA’s Chandra X-ray Observatory to confirm the presence of five merging supermassive black holes in different galaxies. This work shows the effectiveness of X-ray data to help find such black hole pairs. This discovery could help scientists better understand how giant black holes grow and how they may produce the strongest gravitational wave signals in the Universe.