by Fast radio bursts (FRBs) are intense, short-lived bursts of radio waves coming from outside the Milky Way that can emit the same amount of energy in just a few thousandths of a second that the sun takes three days to emit.
However, despite their power and the fact that around 10,000 FRBs may erupt in the sky above Earth every day, these bursts of radio waves remain a mystery. One of the biggest puzzles about FRBs is why most flash once and then disappear and a tiny minority (less than 3 percent) flash again. This has led scientists on a quest to discover the mechanisms that launch FRBs. Some even believe that different celestial objects can produce both repeated and non-reproduced FRBs.
Scientists from the University of Toronto used the Canadian Hydrogen Intensity Mapping Experiment (CHIME) to focus on the properties of polarized light associated with 128 non-repeating FRBs. This showed that the one-time FRBs appear to originate in distant galaxies much like our own Milky Way, compared to the extreme environments of their reborn cousins. The results could bring scientists closer to finally overcoming the celestial answer to FRBs.
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“Until now, when we thought about FRBs, we just looked at them in the same way that we would look at a star in the sky, thinking about how bright it is, maybe finding out how far away it is , things like that,” lead research author Ayush Pandhi, Ph.D. student at the Dunlap Institute of Astronomy & Astrophysics and the David A. Dunlap Department of Astronomy & Astrophysics at the University of Toronto, told Space.com. “However, FRBs are special because they also emit polarized light, meaning that the light coming from all these sources is directed in one direction.”
The main difference about this research is that it really drilled down into the investigation of polarized light.
Polarized light is made up of waves that are oriented in the same way — vertically, horizontally, or at an angle between those two directions. Changes in polarization could explain the mechanism that sent the FRB and thus reveal its source. Polarization can also reveal details about the environments the FRB had to traverse before reaching our detectors on Earth. This study was the first large-scale look at the 97% non-repeat FRBs in polarized light.
There is a gap in non-repeat FRB research because it is much easier to observe repeated FRBs as astronomers already know where they are going to occur, meaning any radio telescope can be pointed at the patch of sky that and wait. With FRBs that don’t repeat, astronomers need a telescope that can look at a large area of the sky at the same time because they don’t really know where the signal is coming from.
“They could pop up anywhere in the sky. CHIME is unique in that sense because it looks at such a large patch of the entire sky at the same time,” said Pandhi. “Also, people haven’t looked at that polarization yet because it’s much harder to detect on a purely technical level.
“Other studies of polarization have looked at maybe 10 non-repeat FRBs, but this is the first time we’ve looked at more than 100. It allows us to rethink what we think FRBs are and what (see how repetitive and non-repetitive). FRBs can be different.”
To repeat or not to repeat?
In 2007, astronomers Duncan Lorimer and David Narkevic, who was Lorimer’s student at the time, discovered the first FRB. It was a burst of energy that is not repeated now commonly known as the “Lorimer burst.” Five years later, in 2012, astronomers discovered the first repeating FRB: FRB 121102. Then, gradually, more repeating bursts became apparent.
Astronomers naturally wonder if there is a different phenomenon behind these two types of FRBs. And Pandhi’s team actually found that non-repetitive FRBs seem to be quite different from repeating FRBs, as most of them appear to come from galaxies like our own Milky Way.
Although the origin of FRBs is shrouded in mystery, these bursts of radio waves can act as messengers of the environments they pass through as they race to Earth. That information is encoded in their polarization.
“If the polarized light passes through electrons and magnetic fields, the angle at which it is polarized rotates, and we can measure that rotation,” Pandhi said “So if an FRB passes through more matter, it will rotate more . If it goes through less, it will rotate less.”
Since the polarization of unreconstructed FRBs is smaller than that of reconstructed FRBs, the former appear to pass through less material or weaker magnetic fields than the latter. Pandhi added that while repeated bursts of radiation appear to come from more extreme environments (such as the remnants of stars that died in supernova explosions) their non-repeating brethren appear to arise in slightly less violent environments.
“Non-recurring FRBs tend to come from environments with weaker magnetic fields or fewer objects around them than repeating FRBs,” continued Pandhi. “So it appears that the repetition of FRBs is a bit more in that sense.”
Are neutron stars out of trouble?
One of the biggest surprises of this research for Pandhi is that the polarization of non-repeating FRBs seems to clarify one of the main suspects behind their launch: highly magnetized, rapidly spinning neutron stars, or “pulsars .”
“We know how pulsars work and we know the types of polarized light we expect to see from a pulsar system. Surprisingly, we don’t see many similarities between FRBs and pulsar light,” said Pandhi. “If these things are coming from. the same type of object, you might expect them to have some similarities, but they actually seem to be quite different.”
As for finding out what sends FRBs, Pandhi thinks expanding our understanding of the polarization of these radio bursts could help narrow down theoretical predictions.
“If we’re confused between different theories, we can now look at the polarized light and say, ‘OK, so does this rule out any theories that we haven’t already ruled out?'” he said. he. “It provides another parameter, or even a few extra parameters, to help us rule out theories about what they might be until we have one that sticks.”
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Pandhi went on to explain that this study laid the groundwork for future FRB investigations; he himself is working on a way to disentangle the polarization of FRBs that occurred in the Milky Way from those that occurred in other galaxies and closer to the source of their emissions.
This should help us better understand the mechanisms behind the launch of FRBs, but for Pandhi, the mysterious nature of these cosmic bursts of energy ensures that he will be investigating them for some time to come.
“I mean, what’s more mysterious than explosions that happen thousands of times a day across the sky, and you have no idea what causes them?” Pandhi said. “If you’re a little detective who likes to solve mysteries, FRBs are just a mystery that’s just waiting to be solved.”
The team’s research was published on Tuesday (June 11) in the Astrophysical Journal.
