Fast radio bursts are decidedly mysterious astronomical phenomena. Every time researchers think they’ve reached their goal and finally understand the secrets of their origins, a new observation comes to call everything into question. This is once again the case today.
The first fast radio burst – a Fast Radio Burst or FRB, as English speakers call them – was observed in 2007. A powerful cosmic explosion that, in just a few milliseconds, hurls into space the equivalent of the energy produced by our Sun in an entire year. Astronomers have therefore been investigating for no less than fifteen years to understand the origins and physical mechanisms behind this extraordinary phenomenon. Fifteen years that their assumptions are constantly challenged by new observations.
Once again today. With observations made in late spring 2021. In 82 hours spread over 54 days, the five hundred meter spherical radio telescope (Fast) installed in China then recorded some 1,863 bursts from a source called FRB 20201124 A. “Largest FRB data sample to date, with bias information from a single source”says Kejia Lee, a researcher at Peking University, in a press release from the University of Nevada (United States).
Recall that recent observations of a fast radio burst in our Milky Way suggest that the source of the phenomenon is to be found in magnetars. Understand, neutron stars accompanied by an incredibly intense magnetic field. However, the origin of the more distant FRBs remains enigmatic. “And these observations bring us back to square one. It’s clear that FRBs are more mysterious than we imagined. Further multi-wavelength observing campaigns will be needed to further unravel the nature of these objects.”comments Bing Zhang, an astrophysicist at the University of Nevada.
A complex and dynamic environment
The astronomers indeed noted irregular and short-lived variations in the magnetic field and the densities of particles evolving near FRB 20201124 A. Variations which increased then decreased during the first 36 days of observation. Variations which then abruptly stopped before, 18 days later, the source finally died out.
“Our work revealed a complex, dynamically changing magnetized environment that had never before been imagined for a fast radio burst. Such an environment is not directly expected for an isolated magnetar. Something else could be near the engine of this FRB. Perhaps a companion signing the existence of a binary system »explains Bing Zhang.
Another surprise is that FRB 20201124A appears to be settled in a region of a metal-rich barred spiral galaxy – much like our Milky Way – in which no significant star-forming activity has been recorded so far. A location that is also not very compatible with the idea of a magnetar type source. What, therefore, definitely relaunch the mystery of fast radio bursts and their sources in galaxies far from ours.