A rare merging of three supermassive black holes has been spotted by a team of astrophysicists in India. They were observing the merging of two galaxies named NGC7733 and NGC 7734 in our celestial neighbourhood when they detected unusual emissions from the centre of the latter and a curious movement of a large bright clump within it, having a different velocity than that of NGC7733.

Inferring that this was a separate galaxy, the scientists named it NGC7733N. There are supermassive blackholes, which are several million solar masses in size, at the centres of galaxies, and these are known as Active Galactic Nuclei. Since they “accrete“ matter, they often have a glow around them which can be observed using light spectroscopy.

Supermassive black holes are difficult to detect because they do not emit any light. But they can reveal their presence by interacting with their surroundings. When the dust and gas from the surroundings fall onto a supermassive black hole, some of the mass is swallowed by the black hole, but some of it is converted into energy and emitted as electromagnetic radiation that makes the black hole appear very luminous.

They are called active galactic nuclei (AGN) and release huge amounts of ionized particles and energy into the galaxy and its environment. Both of these ultimately contribute to the growth of the medium around the galaxy and ultimately the evolution of the galaxy itself, the Ministry of Science and Technology said in a statement.

Led by a team comprising Jyoti Yadav, Mousumi Das, and Sudhanshu Barway from the Indian Institute of Astrophysics, researchers used data from the Ultra-Violet Imaging Telescope (UVIT) onboard the first Indian space observatory ASTROSAT, the European integral field optical telescope called MUSE mounted on the Very Large Telescope (VLT) in Chile and infrared images from the optical telescope (IRSF) in South Africa.