Bizarre radio burst with "heartbeat" rhythm is longest detected by far
Astronomers have detected an extremely strange radio signal from a distant galaxy that pulses with a heartbeat-like rhythm. This signal lasted about 1,000 times longer than other fast radio bursts (FRBs), and had a clear periodic pattern to its pulses.
FRBs are pretty self-explanatory – they’re bursts of radio signals from space that are very fast, lasting mere milliseconds. Some of them are one-hit wonders, while others have been known to repeat, either randomly or in a predictable pattern. Hundreds of FRBs have been recorded since they were first discovered a little over a decade ago.
Now, a team of astronomers using the CHIME radio telescope has detected an FRB like no other. Where all other known FRBs last a few fractions of a second, this new signal, known as FRB 20191221A, lasted several seconds. Weirder still, the radio waves in the signal repeated every 0.2 seconds, a pattern never seen in any other FRB.
“It was unusual,” said Daniele Michilli, lead author of the study. “Not only was it very long, lasting about three seconds, but there were periodic peaks that were remarkably precise, emitting every fraction of a second – boom, boom, boom – like a heartbeat. This is the first time the signal itself is periodic.”
So what could have produced this signal? Despite its uniqueness, the team says the most likely culprit is the leading suspect behind most, if not all, FRBs – a neutron star. Analysis of the pattern of the pulse suggests it came from either a pulsar – a type of neutron star emitting beams of radio waves from its poles – or a magnetar, a neutron star with an extremely powerful magnetic field.
However, FRB 20191221A was more than a million times brighter than any emission ever seen from a pulsar or magnetar in our own galaxy. The researchers hypothesize that this signal might have come from a pulsar or magnetar that’s normally much dimmer, but just so happened to fire off a burst in our direction. This could hint at the environment around it.
“CHIME has now detected many FRBs with different properties,” said Michilli. “We’ve seen some that live inside clouds that are very turbulent, while others look like they’re in clean environments. From the properties of this new signal, we can say that around this source, there’s a cloud of plasma that must be extremely turbulent.”
The team plans to keep watch for more bursts from the object, which might help unravel the mystery.
The research was published in the journal Nature.