The Fast Radio Burst in Our Galaxy Is Officially a Repeater
Astronomers have been trying to work out the nature of Fast Radio Bursts (FRBs) for the last several years, and a series of recent discoveries may have brought us tantalizingly close to unraveling the mystery. Last month, a team announced the discovery of an FRB in our own galaxy, giving scientists a chance to study these bizarre signals up close. The scientific community will have a lot of data on FRBs soon enough — a new study confirms this nearby FRB is repeating.
Fast Radio Bursts were unknown until 2007 when a team discovered the first anomalous signal hiding in data from 2001. Since then, astronomers have spotted dozens of these ultra-high-energy bursts from sources in other parts of the universe. They can outshine entire galaxies, but only for a few milliseconds, and there’s no warning when one will flare — at least, that’s what we used to think. Recently, researchers identified the first repeating example of this phenomenon, known as FRB 121102. It operates on a 157-day cycle, allowing astronomers to gather more data each time it wakes up. Then, teams around the world started to identify other FRBs that repeat. They were all still quite far away, though.
The discovery of a magnetar called SGR 1935+2154 earlier this year was a similarly major advancement in the study of FRBs. Thanks to FRB 121102 and other events, teams around the world started listing magnetars as one of the most probable causes of FRBs. Magnetars are a sub-class of neutron stars with a magnetic field so strong it can disrupt electron orbitals and halt chemistry in normal matter that gets too close. When SGR 1935+2154 “woke up” and started emitting bursts of photons, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and Survey for Transient Astronomical Radio Emission 2 (STARE2) detected an FRB from the same part of space.
While this event was much weaker than the extragalactic FRB events we’ve seen in the past, it has been verified as the same phenomenon and given an official designation: FRB 200428. Since the April 2020 discovery, scientists have kept a close watch over FRB 200428 to see if it might repeat like the more distant FRBs. In May 2020, the Westerbork Synthesis Radio Telescope picked up two more pings from FRB 200428, and the Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) in China detected one fainter signal that same month. Just last month, FRB 200428 woke up again to fire off at least three more FRBs, all of which are still the subject of ongoing study.
This confirms that FRB 200428 is a repeater, but the range of power across the various detections is extremely wide — we’re talking seven orders of magnitude. No one is sure why that’s the case right now, but the new study suggests the mechanism that causes magnetars to emit FRBs has independently variable energy and rate. Alternatively, our ability to detect FRBs might change if the emission cone moves over time. This effect would be more noticeable for a nearby source as opposed to one in another galaxy. The important thing to know is FRB 200428 repeats, and that gives astronomers someplace to point their instruments as we close in on a better understanding of Fast Radio Bursts.