What is Sagittarius A* (Sgr A*)?

About Sagittarius A* (Sgr A*):

• It is a supermassive black hole located at the center of the Milky Way Galaxy.
• It is located in the constellation Sagittarius.
• It has a mass equivalent to four million Suns.
• It has a diameter of around 23.5 million kilometers .
• It is mostly dormant and only occasionally absorbs gas or dust.
• The event horizon of the black hole has a radius of 12 million km.

What is a Black hole?

• A black hole is a region 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, it is difficult to detect a black hole.
• The largest black holes are called "supermassive." These black holes have masses that are more than 1 million suns together.
• Albert Einstein first predicted the existence of black holes in 1916, with his general theory of relativity.

What is the ‘event horizon’ of a Black hole?

• It is the boundary defining the region of space around a black hole from which nothing (not even light) can escape.
• The escape velocity for an object within the event horizon exceeds the speed of light.
• The radius of the event horizon is called the Schwarzschild radius, after the German astronomer Karl Schwarzschild.

 

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Q1) How a black hole created?

Stellar black holes form when the center of a very massive star collapses in upon itself. This collapse also causes a supernova, or an exploding star, that blasts part of the star into space.

Scientists think supermassive black holes formed at the same time as the galaxy they are in. The size of the supermassive black hole is related to the size and mass of the galaxy it is in.

Source: Astronomers discover baby star near centre of Milky Way galaxy