Indian astrophysicists spot rare merger of three jumbo black holes

Source: The Hindu and PIB

What is the News?

Researchers from the Indian Institute of Astrophysics, Bengaluru, have observed three supermassive black holes from three galaxies merging to form a triple active galactic nuclei.

About the Research:

1. Researchers were studying a pair of known galaxies — NGC7733 and NGC7734 — when they detected an unusual bright clump at the centre of one of them. 
2. However, the clump was moving at a different velocity compared to the one in which it was observed. This meant that the clump was not part of the same galaxy, but rather a small, separate galaxy that they named NGC7733N.
3. Based on this, the scientists observed that there are three supermassive black holes from three galaxies merging to form a triple active galactic nuclei(AGN).
4. Moreover, all these three merging black holes were part of galaxies in the Toucan constellation.
   • The constellation Tucana is located in the Southern Hemisphere of the sky.  It is a small constellation. It ranks 48th among the 88 constellations in the night sky. 

About Supermassive Black Holes:

1. A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying. Moreover, because no light can get out, people can’t see black holes. They are invisible.
2. The largest black holes are called “supermassive.” These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center.

What are Active Galactic Nuclei(AGN)?

1. 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.
2. They are called active galactic nuclei (AGN) and release huge amounts of ionised particles and energy into the galaxy and its environment.

Collision of two Black holes:

1. If two galaxies collide, their black hole will also come closer by transferring the kinetic energy to the surrounding gas.
2. The distance between the black holes decreases with time until the separation is around a parsec (3.26 light-years).
3. The two black holes are then unable to lose any further kinetic energy to get even closer and merge. This is known as the final parsec problem.

Significance of three black hole merger:

1. The presence of a third black hole can solve the final parsec problem.
2. The dual merging black holes can transfer their energy to the third black hole and merge with each other.