A black hole is a place in space where gravity pulls so much that even light cannot get out. The gravity is so strong because matter has been squeezed into a tiny space.
Because no light can get out, people can’t see black holes with naked eye or common telescopes. They are invisible. Space telescopes with special tools can help find black holes.
How Big Are Black Holes?
Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain.
Another kind of black hole is called “stellar.” Its mass can be up to 20 times more than the mass of the sun. There may be many stellar mass black holes in Earth’s galaxy, the Milky Way.
The largest black holes are called “supermassive.” These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center.
How Do Black Holes Form?
Scientists think the smallest black holes formed when the universe began.
Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.
Scientists think supermassive black holes were made at the same time as the galaxy they are in.
Source: nasa.gov