Astronomers pick up an intriguing and mysterious radio signal from a distant galaxy

Nail fast radio burst recently discovered has unique properties which, at the same timeprovide astronomers with important clues about the possible causes of these mysterious astronomical phenomena. At the same time, these events call into question one of the few things that scientists thought they knew about these powerful eruptionsas my colleagues and I described in a new study in Nature on June 8, 2022.

rapid radio bursts, or FRBs are extremely bright pulses of radio waves from distant galaxies. They release as much energy in a millisecond as the sun makes for several days . Researchers at West Virginia University detected the first FRB in 2007, and over the past 15 years astronomers have detected about 800 FRBs, with more being discovered every day.

When a telescope captures an FRB, one of the most important features researchers look at is something called scattering. It’s basically a measure of how much an FRB stretches when it hits Earth.

The plasma between stars and galaxies causes all light, including radio waves, slow down, but low frequencies feel this effect more strongly and slow down more than high frequencies. FRBs contain a range of frequencies, so the high frequency light in the burst hits the Earth before the low frequencies, causing scattering. This allows researchers to use scattering to estimate how far from Earth an FRB is born. The more an FRB is stretched, the more plasma the signal must have passed through, the farther the source must be.

The top of this diagram shows six points in radio wave brightness, which are six bursts of FRB190520. The bottom half shows the frequency range for each individual burst. Niu CH, Aggarwal K, Li D et al. , CC BY.

The top of this diagram shows six peaks in the radio waves, which are six bursts from FRB190520. The bottom half shows the frequency range for each of these bursts. Niu CH, Aggarwal K, Li D et al., CC BY

The new FRB that my colleagues and I discovered is called FRB190520. We found it using the 500 meter aperture spherical telescopein China. One interesting thing about FRB190520 is that it is one of only 24 FRBs that repeats, and it does so much more often than the others, producing 75 bursts over a six-month period in 2020.

Additionally, our team used the Very Large Array, un radio telescope in New Mexico to further study this FRB and identified managed to locate its source: a dwarf galaxy about 3 billion light-years from Earth. That’s when we started to realize how unique and important this FRB really is.

First, we discovered that there is a persistent, albeit much weaker, radio signal emitted by something from the same location that FRB190520 came from. Of more than 800 FRBs discovered to date, only one other has a similar persistent radio signal.

Second, since we were able to determine that the FRB originated from a dwarf galaxy, we were able to determine exactly how far this galaxy is from Earth. But this result made no sense. To our surprise, the distance estimate we made using FRB scattering was 30 billion light-years from Earth.a distance 10 times greater than the actual 3 billion light-years of the galaxy.

Astronomers have only been able to determine the exact location, and therefore distance from Earth, of 19 other FRB sources. For the rest of the approximately 800 known FRBs, astronomers must rely solely on scattering to estimate their distance from Earth. In contrast, for the other 19 FRBs with known locations, the estimated dispersal distances are very close to actual distances to their home galaxies. But this new FRB shows that estimates using dispersion can sometimes be wrong, throwing many assumptions out the window.

FRB190520 originated from a small dwarf galaxy 3 billion light years away, marked by the crosses in the larger box with the exact location of the FRB source in the smaller image circle. Niu CH, Aggarwal K, Li D et al. , CC BY

FRB190520 comes from a small dwarf galaxy 3 billion light years away, marked with a cross. Niu CH, Aggarwal K, Li D et al., CC BY

astronomers in this new field they still don’t know what exactly produces FRBstherefore each new discovery or information is important.

Our new discovery raises specific questions, including whether persistent radio signals are common, what conditions produce them, and whether the very phenomenon that produces them The FRB is responsible for emitting the persistent radio signal.

And a big mystery is why the spread of FRB190520 was so much bigger than it should be. Was it due to something near the FRB? Was it related to the persistent radio source? Does it have to do with matter in the galaxy this FRB is from? All these questions are unanswered.

My colleagues will focus on studying FRB190520, using a large number of telescopes different around the world. By studying the FRB, its galaxy, and the space environment surrounding its source, we hope to find answers to many of the mysteries it has revealed.

Other answers will also come from other FRB discoveries in the years to come. The more FRBs astronomers catalog, the greater their chances of discovering FRBs with interesting properties that can help solve the puzzle. these fascinating astronomical phenomena.

*Affiliate researcher in astronomy and astrophysics at West Virginia University.

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