- 3503 - MAGNATARS - new discoveries as to origins? Not all the stars are like our Sun. Some are “Magnetars” that were so large their gravity tried to squeeze them into a blackhole. But if the squeeze does not quite make it to a blackhole instead it leaves an extremely dense body made of neutrons. These Neutron Stars are called “Pulsars” if the spout a radiating beam. If their magnetic field is strong enough they are then called Magnetars.
--------------------- 3503 - MAGNATARS - new discoveries as to origins?
- Our Sun is only one of the billions of stars in our galaxy, the Milky Way. It’s also quite small compared to other stars. Many are at least eight times more massive. A these massive stars have new behaviors.
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- These massive stars influence the structure, shape and chemical content of entire galaxy. When massive stars have exhausted their hydrogen gas fuel and die, they do so in an explosive event called a “supernova“. This explosion is sometimes so strong that it triggers the formation of new stars out of materials in the dead star’s surroundings.
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- Astronomers don’t fully understand how those original massive stars themselves are initially formed. Nearly all the known ‘massive stars” in our galaxy are located very far away from our solar system. They also form in close proximity to other massive stars, making it difficult to study the environment where they take shape.
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- One theory is that a rotating disc of gas and dust funnels materials into the growing star.
Astronomers have recently found that the funneling of matter into a forming star happens at different rates over time.
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- Sometimes the forming star swallows up a huge amount of matter, resulting in a burst of activities in the massive star. This is called an “accretion burst” event. It is incredibly rare, only three such events have been observed, out of all the billions of massive stars in the Milky Way.
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- A “maser” is the microwave (radio frequency) equivalent of “laser“. The word stands for “microwave amplification by stimulated emission of radiation”. Masers are observed using radio telescopes and most of them are observed at centimeter wavelength They are very compact.
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- A maser flare can be a sign of an extraordinary event such as the formation of a star. Since 2017 radio telescopes in Japan, Poland, Italy, China, Russia, Australia, New Zealand and South Africa have been working together to detect a flare stimulated by a burst in the funneling of materials into a massive star.
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- In January 2019, astronomers at Ibaraki University in Japan noticed that one such massive protostar, “G358-MM1“, showed signs of new activity. The masers associated with the object brightened significantly over a short period of time. The theory is that masers brighten when excited by an accretion burst.
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- Follow-up observations with the “Australian Long Baseline Array” revealed something astronomers are witnessing for the first time, a blast of heat-wave coming from the source and traveling through the surroundings of the forming big star. Blasts can last for about two weeks to a few months.
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- Blasts like this were not observed in the previous two accretion bursts in massive stars. This may imply that it’s a different kind of accretion burst. There may even be a “zoo” of accretion burst types, a whole range of different types which act in different ways that may depend on the mass and evolutionary stage of the young star.
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- For the first time, astronomers have definitively spotted a flaring “magnetar’ in another galaxy. These ultra-magnetic stellar corpses were thought to be responsible for some of the highest-energy explosions in the nearby universe. But until this burst, no one could prove it, astronomers reported January 13, 2021.
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- Astronomers have seen flaring magnetars in the Milky Way, but those are so bright that it’s impossible to get a good look at them. Sounds like an oxymoron.
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- Possible glimpses of flaring magnetars in other galaxies may have been spotted before. The first sign of the magnetar arrived as a blast of X-rays and gamma rays on April 15, 2021. Five telescopes in space, including the “Fermi Gamma-ray Space Telescope” and the “Mars Odyssey orbiter“, observed the blast, giving scientists enough information to track down its source: the galaxy NGC 253, or the Sculptor galaxy, 11.4 million light-years away.
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- At first, astronomers thought that the blast was a type of cataclysmic explosion called a short “gamma-ray burst‘, or GRB, which are typically caused by colliding neutron stars.
But the signal looked weird for a short GRB: It rose to peak brightness quickly, within two milliseconds, tailed off for another 50 milliseconds and appeared to be over by about 140 milliseconds. As the signal faded, some of the telescopes detected fluctuations in the light that changed faster than a millisecond.
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- Typical short GRBs that result from a neutron star collision don’t change like that. But flaring magnetars in our own galaxy do, when the bright spot where the flare was emitted comes in and out of view as the magnetar spins.
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- The Fermi telescope caught gamma rays with energies higher than a giga-electron-volt arriving four minutes after the initial blast. There is no way for the known sources of short GRBs to do that.
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- Astronomers think the interaction between those particles and the environment around the magnetar could help explain the blast’s strange appearance. The flare being triggered by a massive starquake, one thousand trillion trillion, or 10^27, times as large as the 9.5 magnitude earthquake recorded in Chile in 1960.
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- The quake led the magnetar to release a blob of plasma that sped away at nearly the speed of light, emitting gamma rays and X-rays as it went. The discovery suggests that at least some signals that look like short GRBs are in fact from magnetar flares.
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- It also means that three earlier events that astronomers had flagged as possible magnetar flares probably were actually from the magnetized stellar corpses, giving astronomers a population of magnetar flares to compare to each other.
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- The finding could have exciting implications for fast radio bursts, another mysterious cosmic signal that has had astronomers scratching their heads for over a decade. Several lines of evidence connect fast radio bursts to magnetars, including another signal coming from within the Milky Way that coincidentally also arrived in April 2020.
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- The apparent frequency of magnetar flares in other galaxies to the frequency of fast radio bursts and found that the rates are similar. That argues that actually, most or all fast radio bursts could be magnetars.
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March 16, 2022 MAGNATARS - new discoveries as to origins? 3503
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