For years, scientists have tried to understand the nature of brief flashes of radio waves called fast radio bursts (FRBs) that are seemingly sent across the universe from an unknown source.
While there have been many theories about the potential origin of FRBs, none of them have established a plausible explanation. This is because researchers have had a hard time knowing where to point their telescopes to observe these radio waves as they happen.
A new study featured in the journal Nature, however, describes an area of the sky near the Auriga constellation where scientists at the Arecibo Observatory in Puerto Rico have been detected at least 11 instances of fast radio bursts over the past four years. These FRBs seem to come from the same astrophysical source in space.
James Cordes, a researcher from Cornell University and one of the authors of the study, said that since the FRBs they examined tended to occur repeatedly, they can eliminate the possibility that these radio waves are simply one-offs formed as a result of evaporating black holes or any other potential sources described before.
He said that it is more likely that fast radio bursts are created by massive energy releases from a neutron star.
What Are Fast Radio Bursts?
A fast radio burst is a phenomenon in space believed to be made of high energy, which often appears in the form of a transient radio pulse that lasts for only a few milliseconds.
Some of the FRBs that have been detected in the past were bright, millisecond flashes that seemed to have come from areas of the sky beyond the Milky Way galaxy.
The duration of an FRB depends on its wavelength, which results in a delay of the burst referred to by scientists as a dispersion measure.
FRBs often have dispersion measures that are significantly larger than what researchers expect from a source within the Milky Way. They are also believed to be spread through the help of plasma.
The first fast radio burst to be recorded was the Lorimer Burst. It was named after West Virginia University astrophysicist Duncan Lorimer, who led a team of researchers in studying the phenomenon in 2007.
The researchers believe that the burst, which only lasted for about 5 milliseconds, could have originated from a part of the universe some 3 billion light-years away from Earth. It was discovered through data gathered by a radio survey of a dwarf galaxy known as the Small Magellanic Cloud in 2001.
As for its possible source, Lorimer and his colleagues speculate that the Lorimer Burst could have been caused by either a collision between two neutron stars, the throes of a dying black hole, or something else they have yet to discover.
It is estimated that as many as 10,000 fast radio bursts flash across the sky every day. However, the briefness of these flashes as well as their unpredictable arrival has made it difficult for scientists to study them. Almost all of the FRBs detected have also been single-flash events only.
In 2012, researchers working at the Arecibo Observatory detected a multi-flash FRB event during a radio survey of the sky. While the repeating burst they found did not show any further activity following the initial observation, it had manifested 10 times in the past based on a review of archived surveys.
Jason W. T. Hessels, an ASTRON scientist from the Netherlands Institute for Radio Astronomy and co-author of the study published in Nature, said that the repeating FRBs detected by Arecibo did not occur regularly.
In one particular case, the researchers observed six successive bright pulses that occurred over 15-minute period. Hessels refers to this event as a “fantastic observation”. The team also saw instances when they weren’t able to detect any FRB activity for hours.
Hessels and his colleagues believe that the nature of the repeating FRBs points to the possibility that some of the radio waves could originate from sources that can produce the bursts more than once. This contradicts the earlier notion that FRBs occur as a result of a cosmic collision between massive objects in space, which would leave them both destroyed in the aftermath.
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