What if I told you the most powerful object in the universe was no bigger than a city? What if I told you it had enough power nothing could escape its grasp, even light? What is this, you ask. A black hole. (Asimov, 1-196)
What is a black hole? A black hole is an old star that has run out of fuel. The pressure created by its fuel keeps the star from collapsing in on itself, but since it runs out of hydrogen, it collapses on itself and becomes so small it literally disappears from the universe. The star must be bigger than a medium sized star otherwise it would just burn out and become a black dwarf star. (Asimov, 1-196)
Now that the black hole has crushed itself, what does it do? Well, a black hole (to be classified as a black hole) has at least three solar masses.
That is, the mass of three solar systems such as our milky way. Its gravitational pull is so great that even light cant escape. It just sits here collecting particles from the universe that passes it. (Asimov, 1-196)
Now what is so hard about studying black holes? They don't emit light. Everything in the universe we have ever studied out in space before "dark matter"(dark matter is matter in the universe that emits no light) was found either produced light or reflected it. Like our planets, they reflect light from our sun, and other stars out there produce their own light. So how do scientists know where they are if we can't see them? With technology that has only
started developing in the last century has helped scientists a lot. To find black holes they use machines that detect radiation from the sky and...