Question

what is the mistery of balckhole

Answer 1

black hole is a place in the space where the gravitational force is so high , that when light enters in it it can't come back.

Answer 2

The story starts in the 1980s, when astronomers found that small (stellar-mass) black holes emit X-ray light that flickers in a curious pattern. At first, this flickering occurs every few seconds; however, the time between each flicker shortens over the course of a few months, eventually stopping completely. 

This "quasi-periodic oscillation" (QPO) was thought to be a result of a phenomenon predicted by Albert Einstein's theory of general relativity — that any object with enough mass, like a black hole, will twist space-time as it spins. Later, scientists calculated that these gravitational vortices will cause the orbits of particles around the black hole to change orientation, leading to the QPO phenomenon. 

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