Radio astronomers have detected the closest repeating fast radio burst (FRB), a mysterious and very brief emission of radio waves whose origin continues to puzzle humanity. The detection comes from galaxy M81, a spiral galaxy less than 12 million light-years away – 40 times closer than the next closest FRB.

FRBs last only thousandths of a second, and most come from galaxies billions of light-years away and only happen once. A few repeat regularly, like the one from M81. Some have been tracked down to their origin, linking the production of FRBs to magnetars, peculiar neutron stars with incredible magnetic fields.

However, the observations of FRB 20200120E, discussed in two papers in the journals Nature and in Nature Astronomy, revealed a surprise. It doesn’t come from a region we would expect a magnetar to be in. It comes from a globular cluster, a spherical group of older stars orbiting M81’s main disk.

“It’s amazing to find fast radio bursts from a globular cluster. This is a place in space where you only find old stars. Further out in the universe, fast radio bursts have been found in places where stars are much younger. This had to be something else,” co-team leader Dr Kenzie Nimmo, from ASTRON and the University of Amsterdam, said in a statement.

Neutron stars are formed when a star 10-25 times the mass of our Sun goes supernova, collapsing in an incredibly compact object around 20 kilometers (12.4 miles) in diameter but with a weight of 1.4 solar masses. Magnetars are a special sub-class of these stars.

Given the size of their original star, they are expected to have burned through their fuel pretty quickly and not exist among a collection of older stars like a globular cluster. These groups tend to form at the same time, so a magnetar is certainly an unexpected finding.

A possibility is that the magnetar came to be in a less “traditional” way. Stars like our Sun are not big enough to go supernova, so when they run out of fuel they leave behind a white dwarf. If these stars can steal enough material from companions, they sometimes collapse under their own weight, go supernova, and turn into neutron stars.

This might be what happened here. Alternatively, the merger of two compact stars might have been the cause of this highly unusual magnetar in this globular cluster. Compact binaries are known to form in clusters.

“Strange things happen in the multi-billion-year life of a tight cluster of stars. Here we think we’re seeing a star with an unusual story,” explains co-team leader Franz Kirsten from Chalmers University and ASTRON.

But it’s not just their location that is surprising – it is also how quickly the bursts last. At just 60 nanoseconds, these are some of the fastest ever FRBs ever detected. That means that they much come from an incredibly small region.

“The flashes flickered in brightness within as little as a few tens of nanoseconds. That tells us that they must be coming from a tiny volume in space, smaller than a soccer pitch and perhaps only tens of metres across,” added Nimmo.

There is still so much that we don’t about FRBs, how they form, and how they work. This work is important to the quest to understand these events and more.

“These fast radio bursts seem to be giving us new and unexpected insight into how stars live and die. If that’s true, they could, like supernovae, have things to tell us about stars and their lives across the whole universe,” Kirsten concluded.