This is an Important Astronomical Anniversary for Joy Division Fans

On November 28, 1967–fifty years ago today–Jocelyn Bell and Anthony Hewish were on duty at the Interplanetary Scintillation Array of the Mullard Radio Astronomy Observatory in Cambridge in the UK when they noticed a strange single coming from…out there, somewhere in the vicinity of the constellation Vulpecula.

It was incredibly precise, repeating exactly every 1.3373 seconds. No matter how long they listened, the signal never wavered, not by even a ten-thousandth of a second. What was it? Bell and Hewish designated the radio sour as LGM-1, which was short for “little green men.” It had to be aliens, right?

Well, no. It was a brand new discovery called a “pulsar,” a collapsed star whose angular momentum spun it into an incredibly fast rotation. These neutron stars send out tightly focused beams of radio radiation that repeat with every rotation.

Bell and Hewish’s discovery became known as CP 1919 (Cambridge Pulsar at RA 19h 19m). It’s also known by the sexy designation PSR J1921+2153.

What does this have to do with music? Twelve years after the pulsar’s discovery, a diagram showing one hundred pulses of CP 1919 became this iconic album cover.