A black hole is a region of Spacetime exhibiting such strong Gravitational effects that nothing-not even particles and electromagnetic radiation such as light—can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a Black Hole.
The boundary of the region from which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally defectable features appear to be observed.
In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiations. With the same spectrum as a black body of a temperature inversely proportional to its mass.
How are Black Holes Formed ?
A common type of black hole is produced by certain dying stars. A star with a mass greater than about 20 times the mass of our Sun may produce a black hole at the end of its life.
From the perspective of the collapsing star, the core compacts into a mathematical point with virtually zero volume. Where it is said to have infinite density. This is called a Singularity.
Where this happens, it would require a velocity greater than the speed of light to escape the object’s gravity. Since no object can reach a speed faster than light, no matter or radiation can escape. Anything, including light, that passes within the boundary of the black hole—called the ‘event horizon‘ —is trapped forever.
One possible mechanism for the formation of supermassive black holes involves a chain reaction of collisions of stars in compact stars clusters that results in the buildup of extremely massive stars, which then collapse to form intermediate – mass black holes.
The star clusters then sink to the center of the galaxy, where the intermediate – mass black holes merge to form a Supermassive black hole.
Are Black Holes Real ?
Don’t let the name fool you : a black hole is nothing but an empty space. Rather, it is a great amount of matter packed into a very small area. A star ten times more massive than the Sun squeezed into a sphere approximately the diameter of New York City.
The result is a gravitational field so strong that nothing, not even light, can escape. In recent years, NASA instruments have painted a picture of these strange objects that are most fascinating objects in space.