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Astronomers have been trying to understand the nature of Fast Radio Bursts (FRBs) in recent years, and a number of recent discoveries may have brought us tantalizing close to unraveling the mystery. Last month, a team announced the discovery of an FRB in our galaxy, giving scientists the chance to study these bizarre signals up close. The scientific community will soon have a lot of data on FRBs: a new study confirms that this neighboring FRB is repeating itself.
Fast Radio Bursts were unknown until 2007, when a team discovered the first anomalous signal hidden in the 2001 data. Since then, astronomers have identified dozens of these ultra-high-energy bursts from sources in other parts of the universe. They can eclipse entire galaxies, but only for a few milliseconds, and there is no warning when one will ignite – at least, that’s what we used to think. Recently, researchers identified the first repeated example of this phenomenon, known as FRB 121102. It runs over a 157-day cycle, allowing astronomers to collect more data each time it wakes up. Then, teams around the world started identifying other FRBs that repeat themselves. But they were all still quite far away.
The discovery of a magnetar called SGR 1935 + 2154 earlier this year was an equally important advance in the study of FRBs. Thanks to FRB 121102 and other events, teams around the world have begun to list magnetars as one of the most likely causes of FRB. Magnetars are a subclass of neutron stars with a magnetic field so strong that it can disrupt electron orbitals and stop chemistry in normal matter that gets too close. When SGR 1935 + 2154 “woke up” and began emitting bursts of photons, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and Survey for Transient Astronomical Radio Emission 2 (STARE2) detected an FRB on the same side of space.
The first ever repeated FRB, located in a dwarf galaxy 3 billion light-years away.
Although this event was much fainter than the extragalactic FRB events we have seen in the past, it was verified as the same phenomenon and given an official designation: FRB 200428. Since the discovery in April 2020, scientists have been closely monitoring FRB 200428 to see if it could repeat itself as the more distant FRBs. In May 2020, the Westerbork synthesis radio telescope detected two more pings from FRB 200428, and the five-hundred-meter aperture spherical radio telescope (FAST) in China detected a weaker signal that same month. Just last month, FRB 200428 woke up again to fire at least three more FRBs, which are still being studied.
This confirms that FRB 200428 is a repeater, but the power range between the various detections is extremely wide: we are talking about seven orders of magnitude. No one is sure why this is the case right now, but the new study suggests that the mechanism that causes magnetars to emit FRBs has independently varying energy and speed. Alternatively, our ability to detect FRBs may change if the emission cone shifts over time. This effect would be more evident for a nearby source than for another galaxy. The important thing to know is the FRB 200428 repeats, and this gives astronomers a place to point their instruments as we get closer to a better understanding of Fast Radio Bursts.
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