What is Sagittarius A* (Sgr A*)?

About is Sagittarius A* (Sgr A*):

• It is a supermassive black hole located at the center of our spiral galaxy, the Milky Way.
• It is mostly dormant and only occasionally absorbs gas or dust, but nonetheless has an estimated mass 4.3 million times that of the sun.
• It is located in the constellation Sagittarius.
• It has a diameter of around 14.6 million miles (23.5 million kilometers).
• It is a strong source of radio waves. Most of the radio radiation is from a synchrotron mechanism, indicating the presence of free electrons and magnetic fields.
• The event horizonof the black hole has a radius of 12 million km (7 million miles).

What is a Black hole?

• A black hole is a region in space where gravity pulls so much that even light cannot 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 "" These black holes have masses that are more than 1 million suns together.
• Albert Einstein first predictedthe 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 velocityfor 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.