Mergers of Three Supermassive Black holes

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Indian researchers have discovered three supermassive black holes merging together to form a triple active galactic nucleus.

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All three merging black holes were part of galaxies in the Toucan constellation.

Toucan Constellation

It is located in the southern hemisphere of the sky. It is visible at latitudes south of 15 degrees between August and October. It is completely below the horizon for anyone north of 30 degrees. It is a small constellation, occupying an area of 295 square degrees.

Scientists were studying the active galactic nuclear (AGN) activity in the two massive barred spiral galaxies NGC7733 and NGC7734 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.
- There are supermassive black holes, which are several million solar masses in size, at the centres of galaxies, and these are known as AGN.
As the third one was a separate galaxy, the scientists named it NGC7733N.

Merger of galaxies

Interaction of galaxies and mergers are the major drivers of galaxy evolution leading to the growth of supermassive black hole bulges and massive galaxies.
One of the most favourable environments for such activity is galaxy groups where galaxies are closely interacting, especially those that have significant reservoirs of cold gas that can be used to fuel star formation and active galactic nuclear (AGN) activity.

What happens when the two galaxies collide?

If the two galaxies collide, their black hole will also come closer by transferring the kinetic energy to the surrounding gas.
The distance between the black holes decreases with time until the separation is around a parsec (3.26 light-years).
The two black holes are then unable to lose any further kinetic energy in order to get even closer and merge. This is known as the final parsec problem.
The presence of a third black hole can solve this problem. The dual merging black holes can transfer their energy to the third blackhole and merge with each other.
Scientists had proven Stephen Hawking’s theory surrounding black holes, which states that it is impossible for a black hole to decrease in size over time. The theorem has been derived from Albert Einstein’s theory of relativity.

Image Courtesy: astronomy

Blackhole

It is a region in space where the pulling force of gravity is so strong that neither matter nor light can escape. This phenomenon occurs when a star is dying.
For anything approaching a black hole, the point of no return is called the “event horizon” and anything that comes within the event horizon will be consumed forever.
Since no light can escape from it, a black hole is invisible.
However, advanced space telescopes can identify black holes by observing the behaviour of material and stars that are very close to black holes.
This hot disk of material encircling a black hole shines bright and against this disk, a black hole appears to cast a shadow.
This is how the photograph of the black hole was achieved.
In 2019, NASA released the first-ever photograph of a black hole and its shadow, which was captured by an international network of radio telescopes called the Event Horizon Telescope (EHT).
- The image shows the shadow of a supermassive black hole in the centre of Messier 87 (M87), an elliptical galaxy some 55 million light-years from Earth.
- This black hole is 6.5 billion times the mass of the Sun.

Source: TH

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