Space junk is any manmade object orbiting Earth that nobody owns, or that nobody controls. It’s litter, basically, and consists of everything from used-up rocket boosters and dead satellites, to nuts and bolts dropped by careless astronauts. Even though space is very big, it’s still becoming enough of a problem that the International Space Station has had to dodge many objects since it was first built, and at least one privately owned communication satellite has been destroyed in a collision (wth the debris from that collision adding to the problem!).
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