- 3566 - MAGNETARS - is this the closest one? The 2022 recently discovered neutron star known as “Swift J1818.0-1607” is estimated to be only about 240 years old.. The young object was spotted on March 12, 2022, when it released a massive burst of X-rays.
--------------------- 3566 - MAGNETARS - is this the closest one?
- A neutron star is an incredibly dense stellar material left over after a massive star goes supernova and explodes. They are some of the densest objects in the universe (second only to black holes). A teaspoon of neutron star material would weigh 4 billion tons on Earth.
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- The atoms inside a neutron star are smashed together so tightly, they behave in ways not found anywhere else. Swift J1818.0-1607 packs twice the mass of our Sun into a volume more than one trillion times smaller.
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- With a magnetic field up to 1,000 times stronger than a typical neutron star—and about 100 million times stronger than the most powerful magnets made by humans this belongs to a special class of objects called “magnetars“, which are the most magnetic objects in the universe.
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- It appears to be the youngest magnetar ever discovered. The light from the stellar explosion that formed it would have reached Earth around the time that George Washington became the first president of the United States.
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- There are over 3,000 known neutron stars discovered but scientists have identified just 31 confirmed magnetars. Because their physical properties can't be re-created on Earth, neutron stars (including magnetars) are natural laboratories for testing our understanding of the physical world.
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- This magnetar is located in the constellation Sagittarius and is relatively close to Eartt, about 16,000 light-years away. Because light takes time to travel these cosmic distances, we are seeing light that the neutron star emitted about 16,000 years ago, when it was about 240 years old.
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- Many scientific models suggest that the physical properties and behaviors of magnetars change as they age and that magnetars may be most active when they are younger. So finding a younger sample close by like this will help refine those models.
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- Though neutron stars are only about 10 to 20 miles in diamerter, they can emit huge bursts of light on par with those of much larger objects. Magnetars in particular have been linked to powerful eruptions bright enough to be seen clear across the universe.
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- The Swift mission spotted this magnetar when it began outbursting. In this phase, its X-ray emission became at least 10 times brighter than normal. Outbursting events vary in their specifics, but they usually begin with a sudden increase in brightness over the course of days or weeks that is followed by a gradual decline over months or years as the magnetar returns to its normal brightness.
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- Astronomers have to act fast if they want to observe the period of peak activity from one of these events. In addition to X-rays, magnetars have been known to release great bursts of gamma rays, the highest energy form of light in the universe. They can also emit steady beams of radio waves, the lowest energy form of light in the universe.
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- X-ray monitoring of a magnetar known as SGR 1935+2154 found that the source has once again became active, this time in the X-ray band.
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Magnetars are neutron stars extremely strong magnetic fields, more than quadrillion times stronger than magnetic field of Earth. Decay of magnetic fields in magnetars powers the emission of high-energy electromagnetic radiation in the form of X-rays or radio waves.
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- This magnetar has a spin period of 3.25 seconds and spin-down rate at a level of 0.0143 nanoseconds/second. These values indicate that the magnetar has a dipole magnetic field with a strength of about 440 trillion G at the pole and characteristic age of some 3,600 years
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- A few years after its discovery this magnetar started a new burst-active phase .April 27, 2020, accompanied by a large enhancement of its X-ray persistent emission. Since this reactivation, SGR 1935+2154 produced numerous X-ray bursts, and also two bright radio millisecond bursts similar to the so-called fast radio bursts (FRBs).
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- The new observations detected X-ray pulsations exhibiting a variable shape switching. It was found that the pulsed fraction decreased from approximately 34 to 11 percent (in the 5–10 kilpoeelectron Volts energy range) over a period of about 10 days.
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- It had X-ray luminosity at a level of 4.0 decillion erg/second, and shortly after it entered an active phase, its X-ray luminosity reached a peak value of approximately 250 decillion erg/s. Therefore, it was the most powerful outburst detected from this magnetar to date.
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- This result is interesting in the context of the physical interpretation of FRBs, bright ms-duration transients coming from distant galaxies. Their brightness temperatures imply a coherent radio emission, inevitably connecting them to pulsars.
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- Using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope, astronomers have detected a bright, millisecond-duration radio burst from this galactic magnetar.
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- Located some 30,000 light years away in the Vulpecula constellation this galactic magnetar exhibits transient radio pulsations. This resulted in the detection of a two-component bright millisecond radio burst on April 28, 2020, similar to FRBs observed at extragalactic distances.
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- The detected event consisted of two sub-bursts lasting 0.585 and 0.355 milliseconds, with the second occurring approximately 0.03 seconds after the first one. The dispersion measure of two burst components was found to be about 332.72 pc/cm^3.
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- The confluence of the two sub-bursts was measured to be 480 and 220 kJy ms. The researchers noted that such values, together with the estimated distance indicate a 400–800 MHz burst energy at a level of 30 decillion ergs, which is brighter than those of any radio-emitting magnetar known to date.
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- This burst was found to be only one to two orders of magnitude below the observed burst energies for typical FRBs, but it could have similar energies to some identified FRBs if they were at their nearest possible distance.
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- Whether the newfound radio burst from SGR 1935+2154 is an FRB remains an open question, but the researchers say that their detection may be helpful in filling the energy gap between the most luminous galactic sources and extragalactic FRBs. This event thus bridges a large fraction of the radio energy gap between the population of galactic magnetars and FRBs, strongly supporting the notion that magnetars are the origin of at least some FRBs.
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May 1, 2022 MAGNETARS - is this the closest one? 3566
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