About Black Hole:

• A black hole is a place in space where gravity pulls so much that even light can not get out. 
• The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.
• 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.

How Big Are Black Holes?

• Black holes can be big or small. 
• Small black holes: 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. 
  • Mass is the amount of matter, or “stuff,” in an object.
• Stellar 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.
• Supermassive black holes: 
  • 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 centre. 
  • The supermassive black hole at the centre of the Milky Way galaxy is called Sagittarius A. 

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.