What is a black hole?
A place where gravity pulls so hard that light can’t even escape. This makes them invisible but special tools find them using the stars around them because they act differently than stars not around black holes. When there is a black hole, stars will orbit them which scientists can observe.
Sizes:
There are black holes that are the size of about one atom, but contain the mass of a mountain.
Stellar black holes are the mass of about 20 suns, there are many of these in the Milky Way.
The largest black holes are the supermassive black holes. There is proof that at the center of every galaxy there is one of these. They can fit about 4 million suns.
How do they form?
The smallest black holes are believed to have formed when the universe began while stellar black holes form when a star collapses on itself, which causes a supernova. Supermassive black holes are believed to have formed when the galaxy they are in formed.
What Would Happen If the Sun turned Into a Black Hole?
Nothing. The Earth would still orbit it as usual and nothing would “fall into” the black hole. Just life would not be possible anymore.
"Famous" Black Holes:
Cygnus-X1: Located 6,500 light years away it is in a binary system that contains a blue supergiant variable star and the x-ray source in the system is supposed to be Cygnus-X1
Sagittarius A: This is the supermassive black hole at the center of the Milky Way that contains the mass of 4 million Suns.
The Event Horizon:
Often called the "Point of No Return", this is where the gravity of the black hole is greater than the momentum of the material in the acceleration disk. Once something crosses the Event Horizon, it is lost to the black hole.
Fun Facts: