The Moon has no atmosphere, which means there is no wind to wear down the surface and no water to wash the footprints off. Since there is no atmosphere, that means the footprints of the Apollo astronauts, spacecraft prints, rover-prints, and discarded material will be there for millions of years. 

           Despite no light being able to escape a black hole’s gravitational pull and being trapped inside of it, people (the naked eye) can’t see black holes. They’re invisible. But, 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. 

         Scientists think supermassive black holes were made at the same time as the galaxy they’re in. 

          When a black hole and a star are close together, high-energy light is made. The kind of light can not be seen with human eyes. Scientists use satellites and telescopes in space to see the high-energy light.

         Another black hole is called “stellar.” Its mass can be up to 20 times more than the mass of the sun. There may be many stellar mass black holes in Earth’s galaxy, the Milky Way!

         The largest black holes are called “supermassive.” 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. The supermassive black hole at the center of the Milky way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns.