Space Junk is human-made object orbiting the Earth without a purpose. Scientists say that about 500,000 pieces of Space Junk orbit in the sky. Any time spaceshuttles travel into space, they leave junk behind. It might be tools, old engine parts, fuel tanks or even an astronaut’s gloves. Satellites eventually wear out and stop working. They, too, become Space Junk. Most of this Space Junk orbits around the Earth. Space Junk is a threat to active satellites and spaceships.