A mysterious radio burst with a pattern similar to a heartbeat has been detected in space.
The signal is thought to have come from a galaxy around a billion light-years away, but the particular location and cause of the burst are unknown. Research reporting the findings was published in the journal Nature on Wednesday.
Fast radio bursts (FRBs) are sudden bursts of radio waves with unknown origins. However, since the discovery of the first FRB in 2007, hundreds of these brief cosmic lights have been recorded emanating from the universe.
Many FRBs emit extraordinarily bright radio waves that last only a few milliseconds before fading completely, and about 10% of them have been seen to have patterns.
A radio telescope called the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, at the Dominion Radio Astrophysical Observatory in British Columbia, Canada, is one tool used to detect the FRBs.
On December 21, 2019, astronomers using CHIME noticed something unusual: a quick radio burst that was “peculiar in many ways,” according to Daniele Michilli, a postdoctoral researcher at the Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research.
The signal, known as FRB 20191221A, might last up to three seconds, which is almost 1,000 times longer than ordinary fast radio bursts.
Michilli was assessing the data coming in from CHIME when the burst occurred. The signal is the world’s longest-lasting rapid radio burst.
“It was unusual,” Michilli said. “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.”
While FRB 20191221A has not yet reappeared, he says that “the signal is formed by a train of consecutive peaks that we determined to be spaced by 0.2 seconds.”
The research team does not know the particular galaxy from which the burst came, and the estimated distance of a billion light-years is “highly uncertain,” according to Michilli.
While CHIME is designed to detect bursts of radio waves, it is less adept at determining their origins.
However, CHIME is being updated as part of a project in which additional telescopes, which are now being built, will observe simultaneously and be able to pinpoint radio bursts to individual galaxies, he explained.
However, the signal contains hints about where it came from and what may have produced it.
“CHIME has now detected many FRBs with different properties,” Michilli said.
“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.”
When the researchers examined FRB 20191221A, they discovered that it resembled the emissions of two different types of neutron stars, or the dense leftovers left after a huge star dies, known as radio pulsars and magnetars.
Magnetars have highly intense magnetic fields, but radio pulsars emit radio waves that appear to pulse when the neutron star rotates. Both star objects emit a signal similar to a lighthouse’s flashing beam.
The quick radio burst looks to be 100,000 times brighter than these emissions.
“We think this new signal could be a magnetar or pulsar on steroids,” Michilli said.
The researchers will keep using CHIME to monitor the skies for new signals from this radio burst and others that emit a similar periodic signal. Radio wave frequency and variation could help astronomers learn more about the universe’s rate of expansion.
“This detection raises the question of what could cause this extreme signal that we’ve never seen before, and how can we use this signal to study the universe,” Michilli said.
“Future telescopes promise to discover thousands of FRBs a month, and at that point, we may find many more of these periodic signals.”