Why in News:
- A rare merging of three supermassive black holes has been spotted by a team of astrophysicists in India.
What is a blackhole
- 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.
- Because no light can get out, people can’t see black holes. They are invisible. Space telescopes with special tools can help find black holes.
- Albert Einstein first predicted the existence of black holes in 1916, with his general theory of relativity.
- The term “black hole” was coined many years later in 1967 by American astronomer John Wheeler.
- Black holes form when massive stars die and their cores collapse. The most common way of black hole formation is when a star runs out of fuel and collapses into its gravitational pull.
- There are four different types of black holes – stellar, intermediate, supermassive, and miniature.
How do we identify them
- A way in which the universe showcases a black hole is when the black hole interacts with its surroundings.
- When the dust particles and matter from the surroundings fall onto a supermassive black hole, it engulfs a part of the surroundings but some of the matter is converted into energy and emitted as electromagnetic radiation that makes the black hole appear very luminous.
- This luminosity can be detected on earth thus, giving more insights into these occurrences.
What did the Indian scientists find?
- Scientists were observing the merging of two galaxies named NGC7733 and NGC 7734 and they detected unusual emissions from the centre of the latter and a 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.
- The scientists observed that there are three supermassive black holes from three galaxies merging to form a triple active galactic nuclei (AGN)
- 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. Active galactic nucleus (AGN) is a small region at the centre of a galaxy that emits a prodigious amount of energy in the form of radio, optical, X-ray, or gamma radiation or high-speed particle jets.
- A supermassive black hole is the largest type of black hole, with mass on the order of millions to billions of times the mass of the Sun.
Significance of this finding
- It can solve the final parsec problem
- If two galaxies collide, their black hole will also come closer by transferring the kinetic energy to the surrounding gas. The distance between the blackholes 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 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.
- Many Active Galactic Nuclei (AGN, supermassive black hole at the centre of a galaxy) pairs have been detected in the past, but triple AGN are extremely rare, and only a handful has been detected before using X-ray observations.
Will the sun become a blackhole?
- The Sun would need to be about 20 times more massive to end its life as a black hole. In some 6 billion years it will end up as a white dwarf — a small, dense remnant of a star that glows from leftover heat. The process will start about 5 billion years from now when the Sun begins to run out of fuel.
- The Sun will start to run out of hydrogen in its core to fuse, and it will begin to collapse. This will let the Sun start to fuse heavier elements in the core, along with fusing hydrogen in a shell wrapped around the core. When this happens, the Sun’s temperature will increase, and the outer layers of the Sun’s atmosphere will expand so far out into space that they’ll engulf Earth.
- Subrahmanyan Chandrasekhar, an eminent Indian scientist proved that there was an upper limit to the mass of a white dwarf. This limit, known as the Chandra limit, showed that stars more massive than the Sun would explode or form black holes as they died.
- In 1983, Subrahmanyan Chandrasekhar was awarded the Nobel Prize in Physics for his work on the physical processes involved in the structure and evolution of stars.
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