- 3214 - FAST RADIO BURSTS - closer to the source? A “fast radio burst” was detected from within our Milky Way galaxy for the first time. We may be closer to uncovering its origin. What's causing these fast radio burst?
------------------ 3214 - FAST RADIO BURSTS - closer to the source?
- Last year on April 28, 2020, two ground-based radio telescopes detected an intense pulse of radio waves. It only lasted a millisecond but it was a major discovery, representing the first time a fast radio burst (FRB) had ever been detected so “close to Earth“.
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- Located just 30,000 light-years from our planet, the event was firmly within the Milky Way. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the Survey for Transient Astronomical Radio Emission 2 (STARE2) had no problems picking it up.
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- Until this encounter all FRBs had been observed outside our galaxy, billions of light years away. This discovery was the most energetic radio blast that astronomers have ever recorded in the Milky Way.
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- FRBs were first discovered in 2007, when astronomers were studying data taken by the Parkes radio dish in Australia.
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- FRBs have been and gone in the blink of an eye despite being 100 million times more powerful than the sun. They can release as much energy in a few thousandths of a second as the sun releases in 100 years. Ideally, astronomers would discover an object and focus one or more different telescopes at it, but the short duration nature of these bursts removes any such opportunity.
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- Astronomers have still succeeded in building up a bank of knowledge about FRBs, most of which has been based on the dozens of recorded events from beyond our own galaxy. We know they are bright flashes of radio light lasting for microseconds to milliseconds. All-sky searches for them also suggest that thousands of these bursts occur in the sky every day.
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- We also know that most of them come from billions of light-years away. Models have been proposed to explain the origins of FRBs, ranging from neutron stars ------ to white dwarfs ------- to cosmic strings.
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- Neutron stars are no more than a few hundred kilometers in size. Yet they are the most likely sources since they are both very small and very energetic.
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- This FRB discovered in the Milky Way is now helping astronomers to firm up such theories. This observational evidence is now suggesting that the origin of FRBs is very likely a “magnetar“, a type of young neutron star born from the embers of supernovas with a magnetic field 5,000 trillion times more powerful than Earth’s, thereby making them the universe’s most powerful magnets.
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- Magnetars are known to emit high-energy electromagnetic radiation, notably gamma rays and X-rays. Both of these erupt in short-lived flares, and there has been speculation that radio waves could be emitted in such a process that would pinpoint magnetars as the source for FRBs.
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- When this latest FRB was discovered in our galaxy, “FRB 200428“, it was found to have originated in the constellation of Vulpecula, which just so happens to be where the galactic magnetar “SGR 1935+2154” is located. It was also accompanied by a burst of X-rays that further excited astronomers.
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- The first detection of X-rays from that sky region came the day before CHIME and STARE2 discovered FRB 200428.
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- The FRB came from the direction of a known magnetar within our galaxy and the radio burst happened at exactly the same time as an X-ray burst coming from the same magnetar.
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- CHIME is based in the Dominion Radio Astrophysical Observatory in Canada, it’s a novel radio telescope with no moving parts, and it has a high mapping speed thanks to its 200-square-degree field of view and broad frequency range of between 400 MHz and 800 MHz.
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- It observes a large area and can monitor all magnetars located in the northern sky every day, allowing us to detect a burst as rare as this one.
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- CHIME has a correlator supercomputer processing 13 terabits of raw data per second to produce a radio map of the sky. Between 2007 and 2017 roughly 50 FRBs were detected. In the last two years, CHIME has seen several hundred.
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- Extragalactic magnetars form only one of the proposed models of FRBs. Bursts from known magnetars in our own galaxy have never been observed to be as powerful as extragalactic ones, and, for the purposes of the study into FRB 200428, astronomers inferred that the burst they detected was 3,000 times brighter than any burst previously observed, thereby making the magnetar model for FRBs more plausible.
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- This burst was still less energetic than most extragalactic FRBs. It may be the case that weaker bursts are more prevalent and that it’s simply a matter of this one being close enough to detect.
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- Magnetars come in two guises: those that have repeating signals, which means they frequently generate the outbursts over and over again, and others that, like FRB 200428, generate more infrequently.
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- How do magnetars do it?"
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- It remains important to discover what powers an FRB to emit such energy? Perhaps electrons interacting with magnetic fields creating an enormous ‘engine’ of energy.
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- Astronomers will also continue to look at how X-ray emissions and these bright bursts of energy are able to occur at the same time. Whether or not all FRBs are created through the same mechanism is an outstanding question. What is your theory?
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- July 6, 2021 FAST RADIO BURSTS - closer to the source? 3214
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--------------------- --- Tuesday, July 13, 2021 ---------------------------
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