The joint research team of NAOJ and other research institutes succeeded in observing a very close binary black hole just before its merger. Recent observation results provide possible evidence that a supermassive black hole with billions of times the mass of the Sun exists in the center of active galactic nuclei. In 2003, the joint research team made the discovery of a binary black hole in the center of 3C66B, which is a giant radio galaxy and a giant elliptical galaxy, by observing the orbital motion of the central core in the galaxy. The team conducted further detailed observations at millimeter wavelengths and identified that the binary black hole will merge in about 500 years. This will demonstrate the interesting possibility of black hole collisions to form a supermassive black hole in the process of evolution, one of the most spectacular natural phenomena in the universe.

In galaxy formation, it is thought that galaxy mergers repeatedly occur to form a giant elliptical galaxy. This scenario will be proactively supported by the discovery of the very close binary black hole in the center of the giant elliptical galaxy and just before the collision.