- 4518 - FAST RADIO BURSTS - what causes them? - What's more mysterious than explosions happening thousands of times per day all over the sky, and you have no idea what's causing them? Fast radio bursts (FRBs) are intense, short-lived blasts of radio waves hailing from beyond the Milky Way that can emit the same amount of energy in just thousandths of a second that the sun takes three days to emit.
------------------------------- 4518 - FAST RADIO BURSTS - what causes them?
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- Despite their power and the fact that
around 10,000 FRBs could erupt in the sky over Earth every day, these blasts of
radiowaves remain mysterious. One of the biggest puzzles surrounding FRBs is
why most flash once and then disappear while a tiny minority (less than 3
percent) repeat the flash.
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- This has led scientists on a quest to
discover the mechanisms that launch FRBs. Some even believe different celestial
objects can produce both repeating and non-repeating FRBs.
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- The Canadian Hydrogen Intensity Mapping
Experiment (CHIME) to focus on properties of polarized light associated with
128 non-repeating FRBs. This revealed the one-off FRBs seem to originate in
faraway galaxies that are much like our own Milky Way, as opposed to the
extreme environments that launch their repeating cousins. The results could
bring scientists closer to cracking the lingering celestial puzzle of FRBs at
last.
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- So far, when we've thought about FRBs,
we've only looked at them in the same way that we would look at a star in the
sky, thinking about how bright it is, maybe figuring out how away far it is,
things like that. However, FRBs are
special because they also emit polarized light, meaning the light coming from
these sources is all oriented in one direction.
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- Polarized light is made up of waves that are
orientated in the same way, vertically, horizontally, or at an angle between
those two directions. Changes in polarization could explain the mechanism that
launched the FRB and thus reveal what its source was. Polarization can also
reveal details about what environments the FRB needed to traverse before
reaching our detectors on Earth. This study represented the first large-scale
look at the non-repeating 97% of FRBs in polarized light.
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- There has been a gap in non-repeating FRB
research because it is much easier to observe repeating FRBs as astronomers
already know where they are going to occur, meaning it is possible to point any
radio telescope at that patch of sky and wait. With non-repeating FRBs,
astronomers must have a telescope that can look at a large area of the sky all
at once because they don't really know where the signal will come from.
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- They could pop up anywhere in the sky.
CHIME is unique in that sense because it looks at such a large patch of the sky
all at once. Also, people have not
really looked at that polarization yet because it's much harder to detect just
on a technical level.
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- Other studies have looked at the
polarization of 10 non-repeating FRBs, but this is the first time where we've
looked at more than 100. It allows us to reconsider what we think FRBs are and
see how repeating and non-repeating FRBs may be different.
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- In 2007 a non-repeating burst of energy is
now commonly referred to as the "Lorimer Burst." Five years after
this, in 2012, astronomers discovered the first repeating FRB. “FRB 121102”. Then, more
repeating bursts gradually revealed themselves.
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- Astronomers naturally wonder whether there
is a different phenomenon behind these two types of FRBs. Non-repeating FRBs seem to be a little
different from repeating FRBs, as most of the former seem to come from galaxies
like our own Milky Way.
-
- While the origins of FRBs are shrouded in
mystery, these bursts of radiowaves can act as messengers of the environments
they pass through while racing to Earth. That information is encoded in their
polarization.
-
- If the polarized light passes through
electrons and magnetic fields, the angle at which it's polarized rotates, and
we can measure that rotation. So if an
FRB passes through more material, it'll rotate more. If it passes through less,
it'll rotate less.
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- The fact that the polarization of
non-repeating FRBs is less than that of repeating FRBs indicates the former
seems to pass through less material or weaker magnetic fields than the latter. While repeating blasts of radiation seem to
be coming from more extreme environments (like the remains of stars that have
died in supernova explosions) their non-repeating brethren seem to emerge in
slightly less violent environments.
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- Non-repeating FRBs tend to come from
environments that have either weaker magnetic fields or less stuff around them
than repeating FRBs. So repeating FRBs
seem to be a little bit more extreme.
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- The polarization of non-repeating FRBs
seems to clear one of the major 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. -
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- Surprisingly, we don't see that much
similarity between FRBs and pulsar light.
If these things are coming from the same type of object, you might
expect that they have some similarities, but it seems that they're actually
pretty different.
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- Is there a way to disentangle polarization
of FRBs that occurred in the Milky Way from those that occurred in their other
galaxies and closer to the source of their emission? This should help us better understand the
mechanisms behind the launch of FRBs.
-
- What's more mysterious than explosions
happening thousands of times per day all over the sky, and you have no idea
what's causing them? FRBs are just a
mystery that is just begging to be solved.
-
-
July 1, 2024 FAST RADIO
BURSTS - what causes them? 4518
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--------------------- --- Tuesday, July 2, 2024
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