Fast Radio Bursts (FRBs) are extremely powerful and extremely brief emissions of light from unknown sources. We have only known about them for less than two decades, and many questions remain about them. Scientists have recently reported the discovery of the closest one coming from a different galaxy just 11.7 million light-years from us in the galaxy M81.
The observations, published in The Astrophysical Journal Letters, describe FRB 20200120E as a repeating FRB, meaning that several pulses have been discovered from the direction of M81. Now a new analysis goes further – it is not only the closest extragalactic FRB (we had one in our galaxy recently), it is also coming from a peculiar place: a globular cluster.
Globular clusters are tightly bound collections of stars that tend to orbit galaxies in their halo, the spherical region surrounding the main disk. FRBs are believed to be caused by young, extremely magnetic neutron stars known as magnetars and since globular clusters are instead made of older stars, the researchers were taken aback by the finding.
“We’ve found a fast radio burst in a globular cluster! This is definitely not a place fast radio bursts are expected to live,” co-author Dr. Bryan Gaensler, Director of the Dunlap Institute for Astronomy and Astrophysics, said in a tweet about the discovery. “Just what is going on??”
The paper detailing the discovery is available on ArXiv and has been submitted for publication. The team has a few proposed scenarios for finding the possible source of an FRB in a globular cluster. Instead of a magnetar formed in a core-collapse supernova (when a star exhausts its fuel and collapses on itself), the team suggests alternative scenarios for the formation of the possible magnetar powering the FRB. It could come from a white dwarf that has stolen material from a companion and collapsed into a magnetar. Or maybe it was via the merger of two compact stars that such a magnetar came to be.
FRBs are not fully understood, and while the magnetar explanation is the one that seems by far the most likely scenario, maybe something different might be at work here. The alternative hypotheses suggested by the team suggest another type of neutron star – a millisecond pulsar – as a possible culprit. Or maybe it’s a binary system causing the radio pulses.
What’s exciting is that since the FRB 20200120E is 40 times closer than any other known FRBs, it can be investigated in detail, and its nature – and maybe more insight into FRBs in general – can be gained from it.