The paper on this discovery, published earlier this month, marked the end of formal observations in February. Like so many people this year, Li has spent most of her days at home, rarely venturing beyond the walls of her small apartment in Bonn, Germany, but the Canadian observatory continues to scan the skies, catching the fleeting FRBs as little smudges of black against a plot of white noise. When Li and I spoke this week, she told me she’s still checking—and the rhythm is still there.
Read: What’s better than one mysterious cosmic signal?
The discovery is an intriguing addition to a growing inventory of knowledge in a field whose earliest evidence was almost dismissed as a fluke. The first FRB was discovered in 2007, buried deep in archival data of a telescope in Australia, while astronomers were looking for another astrophysical phenomenon. The signal was thought to be a telescope artifact, a trick of light masquerading as a cosmic curiosity. And then similar signals started showing up in observations at other telescopes.
Astronomers accepted that they had detected a real event, but they still thought FRBs were one-offs. The flashes were so intense, even after crossing unfathomable distances in space, that whatever had produced them seemed unlikely to survive the cataclysm. But then astronomers found a repeater, a source of FRBs capable of erupting again and again, sometimes several times in less than a minute.
When astronomers managed to trace an FRB to its home galaxy for the first time, they found a small, lively galaxy, where new stars blinked into existence more than 100 times faster than in our own Milky Way. So FRBs must come from these kinds of environments, they thought. But then astronomers found that some FRBs originated in larger, mellower galaxies too.
Read: A burst of light unlike any captured before
“It seems like every time the scientific community converges on a possibility of what FRBs might be, some other observation happens that throws all these speculations out the window,” Kaitlyn Shin, an astrophysics graduate student at MIT who worked on the discovery of the pattern-bearing FRB, told me. “Now all the other theories going forward have to find a way to account for this periodicity.”
And not just from the FRB that Shin and Li’s team found, either; a different team reported this month the discovery of another signal that pulses in a much longer pattern—a 157-day cycle, with 90 days of bursts, followed by 67 days of silence. Many other FRB sources might also follow distinct rhythms, but telescopes just haven’t observed them long enough to spot the tempo.
The nature of the objects that produce FRBs remains a mystery, but astronomers are collecting clues. The most important one to date appeared just two months ago—2020 has been a great year for FRBs, truly—when the observatory Li works with detected an FRB-like event inside our very own galaxy. The flash came from an astrophysical object called a magnetar, an ultramagnetic type of neutron star, the leftover core of an aging star.