These flashes from pulsars are especially bright at radio wavelengths, so their signals can be recorded using radio telescopes. A radio telescope works similar to a radio in your car—its antenna focuses radio waves from space onto a point where they can be detected and turned into an electric signal, which can then be converted into sound. We used the Mark II radio telescope of the Jodrell Bank Observatory at the University of Manchester for our recording.

The album cover shows 80 wiggly lines, which correspond to 80 flashes of radio waves from B1919+21, as the neutron star made 80 turns in 107 seconds. Unlike lighthouses on Earth, each flash is unique. Some flashes are bright—these are denoted in the image by their large spikes—and some are dim. The shape of the pulses is ever-changing. At first glance, they seem irregular and chaotic, but our new imaging reveals some order in the chaos. It’s the same number of pulses from the same pulsar and observed at the same frequency as the diagram from the album cover, but in the image below, a diagonal pattern of stripes emerges. When the original signal was recorded, it was not known why some pulsars showed this kind of pattern. We now believe that the radio waves are produced by particles that shoot away from the neutron star at nearly the speed of light. The particles are created by electric discharges between the ionized gas surrounding these objects and the surface of the star itself. So, in essence, the radio waves on the album cover and in our new imaging are caused by lightning in outer space, observed many light years away. A “weather map” can help visualize the vast lightning systems that circulate the magnetic poles of pulsars. The pattern of their lightning changes continuously, and the shape of the observed pulses appears somewhat erratic—but observing over a longer period allows a pattern to emerge.

Four decades after the release of the Unknown Pleasures album, we now understand much better what those wiggly lines on its cover mean. But many questions remain about these enigmatic objects, which in many respects are nature’s most extreme creation. Something that remained true for all these years is that pulsar recordings push us to explore the limits of our understanding of the laws of physics.

Patrick Weltevrede is a lecturer in pulsar astrophysics at the University of Manchester. This post was originally published on The Conversation.