Theory of Black Holes
A black hole is an area in space with an incredibly strong gravity. This gravity pulls in everything that gets close and nothing can escape from a black hole. Black holes have great amounts of material packed in very tightly. That’s why they are remarkably heavy for their size. They are called “black” because they are invisible. Because no one can see black holes, they are hard to find.
A black hole can be formed when a huge star uses up its fuel. The gravity crushes the star smaller and smaller, and it becomes a black hole. Scientists believe that a huge black hole lies at the center of nearly every galaxy.
The German astronomer Karl Schwarzschild predicted the existence of collapsed stellar bodies that would not emit any radiation. Such cosmic bodies were named black holes about 50 years later.
As first theorized, black holes are formed by the collapse of a massive star into a body only a few miles in diameter, with infinite density and volume and having extraordinarily strong gravity. The pull of gravity is so great that no light can escape. Since a black hole cannot be seen, it can be detected only by gravitational pull on nearby matter, and by the energy released when matter falls into the black hole.
Many astronomers believe that the first stellar black hole was detected in 1971 in the Cygnus constellation. Some astrophysicists believe that there are nonstellar black holes, cosmic bodies that were formed during the origin of the universe or that are still being formed by the collapse of huge amounts of interstellar gas. It is believed that a supermassive black hole exists at the center of the Milky Way. Its mass is believed to be at least four million times that of the sun.
Very small black holes are predicted by theory to be short-lived. Only large black holes are long-lived enough to swallow millions of suns’ worth of mass.