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Artist concept of black hole pulling a blue star

Flickering black hole observed by astronomers in great detail

Astronomers have observed a flickering black hole in the Milky Way in an amazing detail with the help of a high frame-rate method that has helped to understand the dynamics of these cosmic objects. MAXI J1820+070, the black hole was discovered in 2018. It is nearly 7 times the weight of Sun and is at a distance of 10000 light years from Earth. The findings appear in the Monthly Notices of the Royal Astronomical Society journal. 

In comparison to other black holes, it ways much lesser as the “lightest” black hole has a mass of 5 Suns. Besides this, it is flickering and emits X-rays and visible radiation as it consumes matter from a surrounding star. 

Small black holes are normally very hard to observe. The supermassive black hole at the centre of the Universe, Sagittarius A*, although quiet is easier to view since we can observe the orbits of the objects around it. Sgr A* weighs nearly 4 million times that of Sun, acting as the centre of a huge system. But a black hole that weighs only 7 times that of Sun would not have many orbiters. Several stars are in a binary system, where the black hole can consume material from their companions. 

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Astronomers think that this is occurring with MAXI J1820+070 where it is consuming matter from its companion star, the material forming an accretion disc around it in which frictional and magnetic forces compress it producing a high amount of heat. This process results in flickering electromagnetic radiation which has been captured by researchers at a frame rate of 300 fps in optical light with the help of HiPERCAM on Gran Telescopio Canarias and X-rays from NICER observatory, NASA on the International Space Station. 

John Paice, astronomer at the University of Southampton said that the movie was created using real data, although slowing the speed by 10 times so that the rapid flares can be differentiated by the human eye. He added that the material surrounding the black hole can be observed to be bright enough to outshine the star which is being consumed. The fastest flickers last only few milliseconds which is more than the rays from hundred Suns emitted in a blink. 

This approach helped to track both radiation types where rise in one meant a rise in another. However a time gap was observed as the X-ray flashes preceded the optical light flashes by a split second which according to the researchers is an indication of plasma, very close to the black hole. This delay was also observed accreting black holes in 2017 and 2018 clearly indicating a pattern. 

Poshak Gandhi, astronomer at the University of Southampton said that the observation in three systems indicates that it is a characteristic of such black holes. It would help in understanding the flow of plasmas around black holes. This is very important data as these are extreme physical conditions which cannot be replicated in Earth. 

About the author: Kalpit Veerwal
Kalpit Veerwal is a second year Computer Science undergraduate at IIT Bombay. He is well known for being the only person to score 360/360 in JEE (Main). He is registered in the Limca Book of Records for the same. A blogger in his free time, he has also secured top ranks in various exams held in India and the world.

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