Monday, October 3, 2022

Newly discovered fast radio burst challenges what astronomers know about these powerful celestial events

The research brief is a brief about interesting academic work.

big idea

A newly discovered rapid radio burst appears to have some unique properties that are simultaneously giving astronomers important clues about the cause of these mysterious celestial phenomena, while also calling it one of the few things scientists thought were the cause of these powerful Know about flares, as my colleagues and I describe in a new study on June 8, 2022, in Nature.

Fast radio bursts, or FRBs, are extremely bright pulsations of radio waves from distant galaxies. They release the same amount of energy in one millisecond as the Sun in several days. The first FRBs were detected in 2007 by researchers at West Virginia University here. Over the past 15 years, astronomers have detected about 800 FRBs, and more are being discovered every day.

When a telescope captures an FRB, one of the most important features researchers look for is something called dispersion. Dispersion is basically a measure of how much the FRB is spread out when it reaches Earth.

The plasma between stars and galaxies causes all light – including radio waves – to slow down, but low frequencies feel this effect more strongly and more slowly than high frequencies. FRBs have a range of frequencies, so the high-frequency light in the explosion hits Earth before the lower frequencies, causing dispersion. This allows researchers to use dispersion to estimate how far from Earth the origin of an FRB is. The more diffuse an FRB is, the more plasma the signal must have passed through, the further away the source must be.

A diagram with six panels, each showing a spike in a curved line and a shaded frequency diagram.
The top of this diagram shows the six spikes in radio wave brightness that are six bursts from FRB190520. The lower half shows the frequency range of each individual burst.
Niu, C. H., Agarwal, K., Li, D. et al., CC BY

why it matters

The new FRB my colleagues and I discovered is named FRB190520. We found it using the Five Hundred Meter Aperture Spherical Telescope in China. An immediately obvious interesting thing about FRB190520 was that it is one of only 24 repeating FRBs and repeats much more frequently than the others – producing 75 bursts over a six-month period in 2020.

Our team then used the Very Large Array, a radio telescope in New Mexico, to further study this FRB and successfully pinpoint the location of its source – a dwarf galaxy about 3 billion light-years away from Earth. It was then that we started to realize how unique and important this FRB really is.

First, we found that a persistent, though much fainter, radio signal was being emitted by something from the same location as the FRB190520 it came from. Of the more than 800 FRBs discovered so far, only each other has the same permanent radio signal.

Second, since we were able to pinpoint that the FRB came from a dwarf galaxy, we were able to determine how far that galaxy is from Earth. But this result did not make any sense. What is surprising to us is that the distance we estimated using the dispersion of the FRB was 30 billion light years from Earth, which was 10 times larger than the actual 3 billion light years of the Milky Way.

Astronomers have only been able to pinpoint the exact location – and therefore distance from Earth – of 19 other FRB sources. For the remaining approximately 800 known FRBs, astronomers have to rely on dispersion alone to estimate their distance from Earth. For the other 19 FRBs with known locations, the estimated distance from the dispersion is the same as the actual distance to their source galaxies. But this new FRB shows that estimates using dispersion can sometimes be wrong and throw many assumptions out the window.

Image showing the distant bright spots of stars and galaxies.
FRB190520 came from a small dwarf galaxy 3 billion light-years away, marked by the cross hairs in the larger inset with the exact location of the FRB source in the circle in the smaller image.
Niu, C. H., Agarwal, K., Li, D. et al., CC BY

what is not yet known

Astronomers in this new field still don’t know what exactly produces FRBs, so every new discovery or piece of information is important.

Our new discovery raises specific questions, including whether persistent radio signals are normal, what conditions produce them and whether the same phenomenon that produces FRBs is responsible for emitting persistent radio signals.

And a big mystery is why the spread of FRB190520 was greater than it should have been. Was it because of something near the FRB? Was it related to the persistent radio source? Does it have anything to do with the matter of the Milky Way from where this FRB comes? All these questions are unanswered.

what will happen next

My colleagues are going to focus on studying FRB190520 using different telescopes around the world. By studying the FRB, its galaxy, and the space environment around its source, we hope to find answers to many of the mysteries it reveals.

Other FRB discoveries will yield more answers in the years to come. The more FRBs astronomers list, the more likely they are to discover FRBs with interesting properties that may help to complete the puzzle of these fascinating celestial phenomena.

Nation World News Desk
Nation World News Desk
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