Black Holes and the story of their two images

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Black holes are very mysterious things in the universe. Before the discovery of black holes they were just mathematical construct of Einstein's General Relativity also known as Einsteins Theory of Gravity. According to this theory, when the gravity is strong enough, the singularity will form. In other words singularity is the point where some property is infinite. That is a region with a infinite energy density. When this happens, there is a region or notional boundary which is no particles even no light or any other radiation can escape. This region is called the event horizon of a black hole.

Although we cannot see the black hole's event horizon due to no light is emitting, there is a way of watching at glowing gases around the black hole. It creates a bright ring like structure. Although that is the case the surrounded gas and dust particles prevent the sight of seen it. Black holes cannot be seen from optical telescopes and only we can see by using radio telescopes. So low luminosity black holes can be seen by using radio telescopes. 

These images were taken on 2019 and 12th May 2022. The first one which is taken on 2019 is the black hole in the center of the M87 galaxy which is about 55 million light years away. And the latest one is Sagittarius A* Black hole which is located inside the center of our own Milky way galaxy.

 
Two images of the Black holes. Left is the M87* black hole and In the Right side is the Sagittarius A* black hole (Credit: New Scientist Magazine 25th June 2022 Issue and EHT Collaboration) 
 

These two images were taken using EHT (Event Horizon Telescope) which is a planet size radio telescope. EHT is a kind of global network of synchronized radio telescopes around the world to observe black holes. Each and every radio telescopes around the world observe the particular black hole at the same time and collect little data at a time then synthesize in to one image. That is how these above images were created.

M87* black hole is 1500 times massive than Sagittarius A* black hole. Actually Sagittarius A* black hole is around 4.1 millions of solar masses. 


For more details you can go to the following YouTube videos. They are available in both English and Sinhala versions.




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