An international team of scientists led by McGill University researchers has provided the clearest evidence yet that some fast radio bursts (FRBs) - enigmatic, millisecond-long flashes of radio waves from space - originate from neutron stars, the ultra-dense remnants of massive stars that have exploded in a supernova. This finding, based on an analysis of the radio signal of a single FRB, advances our understanding of one of the universe's most perplexing phenomena.
"This result reaffirms long-held suspicions about the connection between FRBs and neutron stars," said Ryan Mckinven, a doctoral researcher in McGill's Department of Physics and corresponding author of the study published in Nature. "However, our findings also challenge popular theoretical models, providing evidence that the radio emission occurs significantly closer to the neutron star than previously thought."
FRBs release as much energy in milliseconds as the sun emits in an entire day. Scientists have detected thousands of these bursts since their discovery in 2007, yet their origins and mechanisms remain elusive. Mckinven's study, conducted using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope, identified a striking similarity between the behaviour of the FRB signal and that of pulsars, a well-studied class of radio-emitting neutron stars.
FRB signals are often highly polarized, meaning that the radio waves predominantly oscillate along a specific, well-defined direction. By examining the polarization of the FRB signal, Mckinven's team observed dramatic changes in its angle over the burst's 2.5-millisecond duration, a characteristic typical of pulsars but rare in FRBs. This distinctive feature initially raised the possibility that the signal might be from a misclassified pulsar within the Milky Way. However, further analysis confirmed the FRB originated in a galaxy millions of light-years away.
"Polarimetry is one of the few tools we have to probe these distant sources," Mckinven explained. "This result will likely inspire follow-up studies of similar behaviour in other FRBs and prompt theoretical efforts to reconcile the differences in their polarized signals."
The research highlights the value of the CHIME telescope, located in Penticton, B.C. It is renowned for its unmatched ability to detect thousands of FRBs daily. The sheer volume of data from CHIME allows scientists to identify unique signals like this one, advancing the broader understanding of FRBs.
"This is a step closer to unravelling a profound cosmic mystery," Mckinven said. "FRBs are ubiquitous, yet their true nature remains largely unknown. Every discovery we make about their origins opens a new window into the dynamics of the universe."
In a study of the same FRB published in the same issue of Nature, lead researcher Kenzie Nimmo of the Massachusetts Institute of Technology provides additional support for the neutron star conjecture.
"We discovered that this FRB exhibits 'twinkling,' similar to how stars appear to twinkle in the night sky. Observing this scintillation indicates that the region where the FRB originated must be incredibly small. We have pinpointed the emission site to a size of less than 10,000 kilometres, despite the FRB originating over 200 million light-years away. This extraordinary precision reveals that the FRB must have come from the intensely magnetic environment surrounding a neutron star, one of the most extreme environments in the universe," said Nimmo.
Together, the Mckinven- and Nimmo-led studies make a strong new case that this FRB - and by extension, others - have their origins in a neutron star.
"These observations provide a rare glimpse into the potential source powering this FRB," said Aaron Pearlman, a Banting Prize Postdoctoral Fellow in McGill's Department of Physics and the Trottier Space Institute, and a co-author of the studies led by Mckinven and Nimmo. "The scintillation pattern and polarization angle swing observed from this FRB are consistent with the expected behavior for a supergiant radio pulse emitted near a highly magnetized, rotating neutron star. These studies offer further evidence that some FRBs may be generated by neutron stars."
About the study
A pulsar-like swing in the polarisation position angle of a nearby fast radio burst by Ryan Mckinven et al., was published in Nature. The Trottier Space Institute at McGill is supported by a generous gift from the Trottier Family Foundation. The CHIME team is led by McGill University, University of Toronto and University of British Columbia, and is operated by funding from the Natural Sciences and Engineering Research Council of Canada, with contributions from various partners.
