Fast radio bursts (FRBs) were discovered in 2007. They are extremely high-energy flashes, usually from far out in the universe. Scientists have now observed more than a thousand fast radio flashes, but it is still unclear where and how they originate.

In the largest study to date, astronomers studied the polarization, or direction of vibration of light, from 128 non-repeating fast radio bursts. The polarization of light is difficult to measure, but it provides insight into the FRBs' production mechanism and contains an imprint of all the magnetic fields the bursts encountered along the way. The researchers used CHIME, a Canadian radio telescope that continuously scans the sky, regularly encountering sudden, one-off events.

The results showed that of the 128 sources, 89 emitted clearly linearly polarized light. At another 29 sources, too little or no polarized light was measured. And at the remaining 10 sources, the signal was too distorted to make any solid statements. Repeating FRBs had been studied previously and tend to emit highly linearly polarized light.

According to Ayush Pandhi, a doctoral candidate at the University of Toronto (Canada) and first author of the study, most of the non-repeating FRBs appear to come from galaxies with modest densities and modest magnetic fields. “These are galaxies that look a lot like our own Milky Way,” he said.

In addition, the researchers compared the polarization of non-repeating FRBs with that of repeating FRBs. “To our surprise, there appeared to be no clearly observable differences in the polarization between non-repeaters and repeaters,” said Ziggy Pleunis (University of Amsterdam and ASTRON) and supervisor of Pandhi. “This is surprising because previous research showed differences in duration and bandwidth between non-repeaters and repeaters, so I expected we would also find a clear difference in polarization.”

According to the researchers, the non-repeating FRBs are more similar to the repeating FRBs than thought previously. “It could be, but now I'm speculating, that repeating bursts and non-repeating bursts have the same origin,” Pleunis said.

The researchers suspect that non-repeating FRBs for example, were first repeating FRBs that have now calmed down. It could also be that non-repeating FRB's are in a less extreme environment and therefore do not burst frequently. Further research will have to reveal the true reason for the distinction.