The night sky is occasionally pierced by short radio waves, like flashes from distant lighthouses. Most are barely noticeable, but sometimes a signal arrives so strong it outshines all others. It was just such a burst, named FRB 20250316A, that the Canadian radio telescope CHIME caught. It was so bright that astronomers decided to check just how likely such an event really is.
To do this, they took all known fast radio bursts from the CHIME catalog and built a statistical model similar to those used to predict rare floods or record heatwaves. It turned out that in terms of peak brightness, FRB 20250316A is a true outlier. On average, such a burst should occur once every 802 years. For comparison, a person won't see anything like it in a lifetime, even if they watched the sky continuously.
The scientists compared this burst to gamma-ray burst GRB 221009A, nicknamed the 'brightest of all time.' It turned out that FRB 20250316A is its radio sibling: an equally exceptional event, but in a different wavelength range. Such rare super-bright bursts could be a separate class of events, born from special conditions in distant galaxies. Or they might just be the extreme tail of the distribution, where nature sometimes throws surprises.
So far, telescopes have been observing for only a few years, and every new record-holder forces us to revise our models. Perhaps even brighter bursts lie ahead, revealing the most extreme processes in the universe.
Fast radio bursts last only a few milliseconds, but in that time they release as much energy as the Sun emits over days or even years.