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On April 10, 2019, the Event Horizon Telescope collaboration released the first successful image of a black hole’s event horizon. The black hole in question comes from the galaxy Messier 87: the largest and most massive galaxy within our local supercluster of galaxies. The event horizon’s angular diameter was measured to be 42 micro-arc-seconds, implying that it would take 23 quadrillion black holes of equivalent size to fill the entire sky.
200-person Event Horizon Telescope (EHT) team revealed in simultaneous press conferences in six countries that it had succeeded in its nearly 20-year quest to image the shadow of a black hole for the first time. The bright ring of light encircling the black hole at the heart of Messier 87, a giant elliptical galaxy 53 million light-years from Earth, appeared largely as expected. Now, the EHT team is eager to sharpen its pictures. That could help them test the predictions of Albert Einstein’s theory of gravity, general relativity, and understand the physics of how black holes feast on the matter that swirls around them and launch powerful jets that can be seen from across the universe.
How was EHT able to construct the image of Black hole?
It’s only because:
- the Event Horizon Telescope has sufficient resolution to see this black hole,
- the black hole is a strong emitter of radio waves,
- and there’s very little foreground radio emissions to contaminate the signal.
What is a Black Hole?
Albert Einstein first predicted black holes in 1916 with his general theory of relativity. The term “black hole” was coined in 1967 by American astronomer John Wheeler, and the first one was discovered in 1971.
There are three types: stellar black holes, supermassive black holes and intermediate black holes.
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. The special tools can see how stars that are very close to black holes act differently than other stars.
Black holes have three "layers" — the outer and inner event horizon and the singularity.
The event horizon of a black hole is the boundary around the mouth of the black hole where light loses its ability to escape.
Once a particle crosses the event horizon, it cannot leave.
Gravity is constant across the event horizon.
The inner region of a black hole, where its mass lies, is known as its singularity, the single point in space-time where the mass of the black hole is concentrated.
How Big Are Black Holes?
Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain. Mass is the amount of matter, or “stuff,” in an object.
Another kind of black hole is called “stellar.” Its mass can be up to 20 times more than the mass of the sun. There may be many, many stellar mass black holes in Earth’s galaxy. Earth’s galaxy is called the Milky Way.They are the most common.
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. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths.
How Do Black Holes Form?
Scientists think the smallest black holes formed when the universe began.
Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.
Scientists think supermassive black holes were made at the same time as the galaxy they are in.
If Black Holes Are "Black," How Do Scientists Know They Are There?
A black hole can not be seen because strong gravity pulls all of the light into the middle of the black hole. But scientists can see how the strong gravity affects the stars and gas around the black hole. Scientists can study stars to find out if they are flying around, or orbiting, a black hole.
When a black hole and a star are close together, high-energy light is made. This kind of light can not be seen with human eyes. Scientists use satellites and telescopes in space to see the high-energy light.
Significance of Black holes
Black holes provide an important tool for probing and testing the fundamental laws of the universe.
All objects exert an attractive gravitational force which depends on their mass. Now, imagine an object with a very large mass which is concentrated into such a small volume that the gravitational field generated is powerful enough to prevent anything from escaping its clutches – even light. This bizarre concept intrigues everyone, in particular physicists who theorise about the nature of matter, space and time, and astrophysicists who look for real black holes out in space. Their study brings together the big ideas in fundamental science: Einstein’s theory of gravity – general relativity; the theory of the very small – quantum mechanics; and the origin and evolution of the universe – cosmology.
Related Topic-
String Theory
In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. It describes how these strings propagate through space and interact with each other. On distance scales larger than the string scale, a string looks just like an ordinary particle, with its mass, charge, and other properties determined by the vibrational state of the string. In string theory, one of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries gravitational force. Thus string theory is a theory of quantum gravity.
String theory is a broad and varied subject that attempts to address a number of deep questions of fundamental physics. String theory has been applied to a variety of problems in black hole physics, early universe cosmology, nuclear physics, and condensed matter physics, and it has stimulated a number of major developments in pure mathematics. Because string theory potentially provides a unified description of gravity and particle physics, it is a candidate for a theory of everything, a self-contained mathematical model that describes all fundamental forces and forms of matter.
