THREAD: Need a break from #BlackFriday, digging @NASA’s #BlackHoleFriday? Perfect, enjoy our Black Hole 101! ☄️
First the basics. A black hole is a region in space where the pulling force of gravity is so strong that light is not able to escape. Because of this, black holes are invisible. Only telescopes with special instruments can help find them.
There are three main types of black holes. The black hole's mass and size determine what kind it is.
The smallest ones are known as primordial black holes. Scientists believe this type of black hole is as small as a single atom but with the mass of a large mountain. 
The most common type of medium-sized black holes is called "stellar." The mass of a stellar black hole can be up to 20 times greater than the mass of the sun and can fit inside a ball with a diameter of about 10 miles.
Did you know dozens of stellar mass black holes may exist within the Milky Way galaxy?
The largest black holes are called "supermassive." These black holes have masses greater than 1 million suns combined and would fit inside a ball with a diameter about the size of the solar system.
Primordial black holes are thought to have formed in the early universe, soon after the big bang.
Stellar black holes form when the center of a very massive star collapses in upon itself. This collapse also causes a supernova, or an exploding star, that blasts part of the star into space.
Scientists think supermassive black holes formed at the same time as the galaxy they are in. The size of the supermassive black hole is related to the size and mass of the galaxy it is in.
If a black hole with the same mass as the sun were to replace the sun, Earth would not fall in. The black hole with the same mass as the sun would keep the same gravity as the sun.
NASA is learning about black holes using information from @NASAHubble,@chandraxray
@NASAFermi, and @NASAspitzer.
@NASAFermi, and @NASAspitzer.
Want to learn more about black holes? Ask a question with #AskNASA #BlackholeFriday. More here on black holes: nasa.gov/black-holes
