In a recently shared image from NASA, a galaxy called NGC 6240 contains two supermassive black holes that are merging. The image consists of new X-ray data from Chandra (shown in red, orange and yellow) combined with an optical image from the Hubble Space Telescope originally released in 2008.
These merging black holes are spaced about 3,000 light-years apart and are seen as the bright point-like sources in the center of the image. These black holes are so close together because they spiral towards each other – a process that started about 30 million years ago.
In 2020, the discovery of two merging black holes was announced, based on Chandra data. Since 2002, there has been great interest in follow-up observations of NGC 6240 by Chandra and other telescopes.
NGC 6240 is a nearby ultraluminous infrared galaxy (ULIRG) in the constellation Ophiuchus. The galaxy is the remnant of a merger between three smaller galaxies.
Scientists say the merging process started about 30 million years ago. It is estimated that the two black holes will eventually float together and merge into a larger black hole in a few tens or hundreds of millions of years.
Pairs of huge black holes are believed to explain some of the unusual behavior seen by fast-growing supermassive black holes, such as the distortion and bending seen in the powerful jets they produce. Merging pairs of huge black holes are also expected to be the most powerful sources of gravitational waves in the Universe.