The cover to Joy Division's 1979 album Unknown Pleasures is incredibly iconic, inspiring everything from tattoos to t-shirts sold at Disneyland. But what you may not know is that this image is actually a diagram from the Cambridge Encyclopedia of Astronomy.

Graphic artist Peter Saville — who also designed the infamously expensive single sleeve for New Order's "Blue Monday" — explains how the band wanted a "comparative path demonstration of the frequency of a signal of a pulsar" as their cover illustration. Watch Saville recall the sleeve's history in the above video.

[Visualized via The Creators Project]