SAGITTARIUS A* (Syllabus: GS Paper 3 – Sci and Tech)

Context: Scientists have uncovered an intermediate-mass black hole at the center of a star cluster in the Milky Way, situated near the supermassive black hole Sagittarius A* (SgrA*).

Sagittarius A* (Sgr A*)

• Location: It is a supermassive black hole located at the center of our spiral galaxy, the Milky Way.
• Mass: It is mostly dormant and only occasionally absorbs gas or dust, but has an estimated mass 4.3 million times that of the sun.
• Constellation: It is located in the constellation Sagittarius.
• Diameter: It has a diameter of around 14.6 million miles (23.5 million kilometers).
• Radio Waves: 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.
• Event Horizon: The event horizon of the black hole has a radius of 12 million km (7 million miles).

Black Hole

• Definition: A black hole is a region in space where gravity pulls so much that even light cannot get out.
• Formation: The gravity is so strong because matter has been squeezed into a tiny space, often occurring when a star is dying.
• Detection: Because no light can get out, it is difficult to detect a black hole.
• Types: The largest black holes are called "supermassive," having masses greater than 1 million suns combined.
• Theoretical Prediction: Albert Einstein first predicted the existence of black holes in 1916, with his general theory of relativity.
• Event Horizon: It is the boundary defining the region of space around a black hole from which nothing (not even light) can escape.