The cover of LIFE magazine from Oct. 21, 1957, shows Smithsonian Observatory scientists working at M.I.T. in Cambridge to try to calculate Sputnik's orbit.

Dmitri Kessel/Time Life Pictures/Getty Images

What is Space Junk?

Space junk got its start in the middle of the twentieth century, at the very beginning of the space race. When the Soviet Union launched Sputnik I, the first satellite in history to go into orbit around the Earth, on Oct. 4, 1957, the world paid attention. Although the satellite was small by today's standards -- it was about the size of a beach ball -- Sputnik still caused a great amount of fear among nations, especially the United States. Along with sparking the space race, the launch worried many Americans because of its association with the nuclear arms race. If the Soviets were capable of putting a satellite into space, they could also strap a nuclear bomb on top and reach a target in a matter of hours.

Since this caught everyone off guard, several countries threw resources into space programs -- the event directly led Congress to create the National Aeronautics and Space Administration, or NASA.

Governments, and now cell phone, television and GPS receiver companies, have launched hundreds of satellites a year since the beginning of the space race. These satellites, along with rockets and other objects sent up into space, make up the majority of space junk. The NASA Orbital Debris Space Program Office also lists these types of objects as examples of space junk:

  • Derelict (abandoned) spacecraft - When spaceships or parts of spaceships no longer work, they're left to float around space indefinitely. It's usually too expensive to retrieve these objects, so they're left there to circle the Earth until they fall back down or collide with other space junk. Tom Ervin/Getty ImagesJim Rollings, Executive Director of the South Florida Science Museum, holds a discarded space shuttle tile from the Space Shuttle Endeavor.
  • Upper stages of launch vehicles - Modern space shuttles are actually a collection of several rockets stacked on top of each other. When space shuttles launch, it usually takes more than one rocket boost to get them high enough into space, and these rockets are fired off in stages. The final stages are called upper stages because they're located near the top of the entire shuttle, and because they fire so late, any material expelled from the spacecraft can get trapped in the Earth's orbit. They're among the largest kinds of space junk.
  • Solid rocket motor effluents - Some space shuttles use solid rocket fuel for propulsion. After launches, some fuel can be left over and will float around in whatever container in which it flew up. This poses a great risk for collisions, because it only creates more space junk after an explosion.
  • Tiny flecks of paint - Although it may be hard to believe, there are potentially millions of tiny pieces of paint floating around Earth's orbit. Heat or impacts with other small particles usually chip off paint specks from spacecraft and turn them into space junk.

How dangerous could all these objects be in space? See the next page to find out.