Yesterday was the 40th anniversary of the release of Joy Division’s Unknown Pleasures. A radio astronomer celebrated by doing this.

When Joy Division released Unknown Pleasures on June 15, 1979, people were a little confused by the packaging. There was no mention of the name of the band nor were there any external liner notes. Instead, the all-black album featured this mysterious graphic.

That is one hundred pulses of a stellar object called a pulsar, specifically one called CP 1919 (technically PSR B1919+21) in the constellation of Vulpecula. It was discovered by a radio astronomer named Jocelyn Bell Burnell on November 26, 1967. It was the first pulsar ever discovered. The image was recorded by Harold Craft in 1970 when he was working on his PhD at the Arecibo Radio Telescope in Puerto Rico. (Read more on the scientific background here.)

The Unknown Pleasures artwork was designed by Peter Savile, Factory Records’ favourite graphic artist. He found the image in The Cambridge Encyclopaedia of Astronomy and was immediately struck by how this dead star was transmitting a signal that will go on forever. All he did was reverse the image into a negative version of what he saw in the book.

To celebrate the 40th anniversary of the album’s release, the boffins at the Jordrell Bank radio telescope in England made another observation of CP 1919 yesterday.

Nothing much has changed. It still has a period of exactly 1.3373 seconds and a pulse wide of 0.4 seconds. Cool, no?

40 years ago today, @joydivision's Unknown Pleasures was released. Its cover featured signals from the first pulsar CP1919. To mark the anniversary, we made this observation of the pulsar earlier today pic.twitter.com/xQfyEm6lLf

— Jodrell Bank (@jodrellbank) June 15, 2019

By the way, there are at least two other pieces of music related to CP 1919. The first comes from the Max Richter Orchestra called “Journey (CP1919)” while the Arctic Monkeys used a sound based on the sound of the pulsar in the video for “Four Out of Five.”