A black hole is a place in space where gravity pulls so much that even light can’t get out. That’s because the matter has been squeezed into a tiny space.
Because no light can get out, people can’t see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.
Try to jump so high that you want to fly right off of the Earth into outer space. What happens? Why don’t you get very far? The gravitational force pulls you back down again very quickly.
You are basically trapped on Earth unless you can find something that can travel at escape velocity away from Earth. This is how our space program works. If you shoot something fast enough, it can escape gravity and make it outer space.
But what if gravity were strong enough to trap light itself? Then you got yourself a black hole.
Black holes can be created by the gravitational collapse of large stars that are at least twice as massive as our Sun. Normally, stars balance the gravitational force with the pressure from the nuclear fusion reactions inside. When a star gets old and burns up all of its hydrogen into helium and then turns the helium into heavier elements like iron and nickel, it can have three fates. The first two fates occur for stars less than about twice the mass of our Sun (and one of them will be our Sun’s eventual fate). These two fates both depend on the fermionic repulsion pressure described by quantum mechanics — two fermions cannot be in the same quantum state at the same time. This means that the two stable destinies for a collapsing star will be:
1. a white dwarf supported by the fermionic repulsion pressure of the electrons in the heavy atoms in the core
2. a neutron star supported by the fermionic repulsion pressure of the neutrons in the nuclei of the heavy atoms in the core
How Do Scientists Know The Black Holes Are There?
A black hole can not be seen because strong gravity pulls all of the light into the middle of the black hole. But scientists can see how the strong gravity affects the stars and gas around the black hole. Scientists can study stars to find out if they are flying around, or orbiting, a black hole.
When a black hole and a star are close together, high-energy light is made. This kind of light can not be seen with human eyes. Scientists use satellites and telescopes in space to see the high-energy light.
And if you were wondering if our Sun can be turned into a black hole, the answer would be simply NO, because the Sun is not a big enough Star to form a Black Hole.
If the mass of the collapsing star is too large, bigger than twice the mass of our Sun, the fermionic repulsion pressure of either the electrons or the neutrons is not strong enough to prevent the ultimate gravitational collapse into a black hole.