An artist impression of orbital debris based on actual density data. However, the debris objects are shown at an exaggerated size to make them visible at the scale shown. (Credit: NASA)

On October 4, 1957, Sputnik I made history as the first satellite to successfully launch into space. But it also marked another milestone: The beginning of space trash.

Space trash or junk is basically any man-made object that exists in space but no longer serves a useful purpose. This includes debris that is released or left behind (like rocket bodies), deactivated satellites that are no longer in use, and even personal items that astronauts accidentally lose—such as a glove, camera or spatula.

“There’s been a pretty steady, exponential rise in the number of objects that space-faring nations have sent into space over the course of the last half century,” says Lisa Ruth Rand, a postdoctoral fellow at the University of Wisconsin-Madison who is writing a book on space trash. “Anytime we launch something into space, for the most part, we’re also generating space junk.”