Newly discovered explosion challenges what science knows about rapid radio eruptions

A newly discovered cosmic radio eruption has unique properties that give scientists important clues to the possible causes of these mysterious astronomical phenomena known as rapid radio eruptions (FRBs).

Next, an optical, infrared and radio image of the FRB 20190520B field. Credit: K. Aggarwal et al.

At the same time, such features challenge what astronomers thought they knew about these powerful explosions, as described in a new study published in the journal nature During this month.

First discovered in 2007, FRBs are extremely bright pulses of radio waves from distant galaxies. In just one millisecond, they release as much energy as the Sun for several days. Over the last 15 years, around 800 FRBs have been observed and this number tends to increase more and more.

According to Kshitij Aggarwal, a researcher at the University of West Virginia, USA, when a telescope captures an FRB, one of the most important properties that scientists look at is something called scattering, which is basically a measure of how stretched a FRB is when it reaches the Earth.

“The plasma that sits between stars and galaxies lowers all light – including radio waves – but low frequencies feel this effect more strongly and slow down more than high frequencies,” Aggarwal explained in an article published on the website. The conversation.

“FRBs contain a range of frequencies, so the high-frequency light from the eruption hits the Earth earlier than the low frequencies, causing scattering,” said the researcher, who is one of the authors of the new study. “This allows scientists to use scattering to assess how far from Earth an FRB was born. The more a FRB is stretched, the more plasma the signal must have passed through, and the longer the source must be.

FRB190520 is a fast repeating radio burst

The new FRB discovered by Aggarwal and his team is called FRB190520. They found it using China’s 500-meter Aperture Spherical Radio Telescope (FAST), also known as “Heaven’s Eye”.

“One immediately interesting thing we noticed about FRB190520 is that it is one of only 24 FRBs that repeats itself, and it does so so much more often than others,” Aggarwal said. “It produced 75 outbreaks over a six-month period in 2020.”

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In the graphs of line a, there is the dynamic burst frequency spectrum with significant evidence of pulse gain. In b are examples of eruptions without significant signs of pulse amplification. Credit: K. Aggarwal et al.

The team then used observations from the Advanced Very Large Array (VLA) radio telescope in New Mexico, USA, to learn more about this FRB and managed to identify the location of its source – a dwarf galaxy. billion light-years from Earth. “It was then that we began to realize how unique and important this FRB really is,” Aggarwal reported.

First, they discovered that there is a persistent, albeit much weaker, radio signal from somewhere in the same place that the FRB190520 came from. “When we were able to identify 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 the scientists’ surprise, the distance estimate they made using FRB scattering was 30 billion light-years from Earth, a distance 10 times greater than the actual 3 billion light-years from Earth.

Astronomers have only been able to determine the exact location – and thus the distance from Earth – of 19 other FRB sources. For the rest of the known FRBs, astronomers have to rely solely on scattering to estimate their distance from our planet.

“For FRBs with known origins, the estimated scattering distances are very similar to the actual distances of their home galaxies,” Aggarwal explained. “But this new FRB shows that estimates using diffusion can sometimes be wrong and throw a lot of assumptions out the window.”

And after

This new discovery raises some questions, such as whether sustained radio signals are common, what conditions produce them, and whether the same phenomenon that produces FRBs is responsible for transmitting the sustained radio signal.

Moreover, according to Aggarwal, it is a big mystery why the spread of FRB190520 was so much greater than it should be. “Was it because of something close to the FRB? Was it related to the persistent radio source? Does it have to do with matter in the galaxy that this FRB is from? All these questions have not been answered, ”said the researcher, revealing that he and his team will focus on studying the phenomenon using several 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 has revealed,” he said.

Further answers may also come from further studies of this and other FRBs in the coming years. The more records astronomers catalog, the greater their chance of discovering FRBs with interesting properties that can help unravel these fascinating astronomical phenomena.

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