A black hole is an astronomic object and its gravitational field is so powerful that anything does not escape its pull, they are invisible because no light can get out in black holes and people can’t see black holes.
There is a boundary around the black hole and it is called an event horizon in which objects can fall, but nothing can come out. Astronomers use Space telescopes with special tools and find out black holes. These special tools can see how stars that are very close to black holes act differently than other stars. Supermassive is known as the largest black hole, 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.
Stellar is another kind of black hole Its mass can be up to 20 times more than the mass of the sun. There may be many, many stellar-mass black holes in Earth’s galaxy. Earth’s galaxy is called the Milky Way. A black hole can reveal its appearance through interactions with other substances. A black hole can be detected by looking at the speed of the group of stars that revolve around a part of the visible space. Alternatively, with a companion star, you can see the gas falling in a relatively small black hole.