95% of the objects in this computer generated simulation of low-Earth orbit objects is “orbital debris”, not satellites. “Space junk” consist of everything from spent rocket stages, lost equipment and defunct satellites to erosion, explosion and collision fragments. NASA estimates there are more than 500,000 pieces of space junk orbiting the Earth (“tens of millions” if you count smaller objects such as coolant, paint particles, and dust from solid rocket motors). The space junk eventually collides with other orbital debris (and potentially satellites) creating even more pieces of dangerous objects orbiting the Earth. As the orbit of the objects declines, they eventually re-enter the Earth’s atmosphere where they hopefully burn up before reaching the ground.
UK researcher, Hugh Lewis predicted that the threat from space debris would rise 50 percent in the coming decade and quadruple in the next 50 years. Currently more than 13,000 close calls are tracked weekly. In 1969, five sailors on a Japanese ship were injured by space debris, probably of Russian origin. In 1997 an Oklahoma woman was hit in the shoulder by a 5.1 in piece of blackened, woven metallic material that was later confirmed to be part of the propellant tank of a Delta II rocket.
According to CNet:
“DARPA is so concerned with the problem that it’s started what it calls the SpaceView program, which seeks to enlist amateur astronomers as sky watchers, helping to track all the debris floating above.”