- 2727 - MAGNETARS - magnetic stars in the heavens? - Magnetars are pulsars that have magnetic fields 1000 times greater that the average pulsar. Pulsars are rotating neutron stars. Neutron stars are what is left over after a large star dies, explodes into a supernova.
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---------------------- 2727 - MAGNETARS - magnetic stars in the heavens?
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- When stars are so massive, 10 to 40 times larger than our Sun they explode when they run out of nuclear fuel. And, they run out of fuel more quickly because they burn nuclear fuel more rapidly than modest size stars.
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- But, what is left over after the explosion is still so massive that its gravity smashes atoms until they collapse on themselves. The atom’s electrons get squeezed into the nucleus’s protons creating a solid neutron star. The star becomes a single atomic nucleus that is 12 miles in diameter, weighing twice as much as our Sun. That is very, very dense matter.
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- These stars all have different names because they are different sizes and that causes different properties. Some of the spinning neutron stars have enormous magnetic fields. We call them Magnetars and 14 of them have been discovered to date. One is in the Large Magellanic Cloud galaxy. A second in the Small Magellanic Cloud galaxy. And, a dozen in our Milky Way Galaxy.
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- How do astronomers measure a magnetic field that is 1000’s of lightyears away?
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- They do not measure it directly. What they can measure is the spin rate of the neutron star. This is done with the light curve showing a blue shift of the light on the side of the star spinning towards us and a redshift of the light on the side of the star spinning away from us.
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- The spin rates of the 14 Magnetars range from 5.16 seconds per rotation to 11.8 seconds per rotation. If these spin rates slow down over time something causes it. The conservation of angular momentum would keep them spinning.
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- If the star has a large magnetic field the magnetic force acts as a friction to slow down the spin rate. The angular momentum loss is converted to magnetic energy gained.
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- Note that these spin rates are very high. A 12 mile diameter neutron star has a circumference of 37.7 miles rotating in 6 seconds means the surface velocity is 22,620 miles per hour.
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- The rotational inertia of a uniform sphere is 2/5 Mass*Radius^2 = .4* 4*10^30 kg * 9,656 meters^2 = 1.49*10^38 kg*m^2.
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-------------- The rotational velocity is 2*pi radians / 6 seconds = 1.05 radians / second.
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-------------- The angular momentum is inertia * velocity = 1.56 10^38 kg*m^2/sec
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- The change in rotational energy converted to magnetic energy allows astronomers to calculate the strength of the magnetic field:
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-------------- Magnetar ------------ 100,000,000,000 Tesla, kilogram / (ampere*sec^2)
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This is within one magnitude of the strength of the magnetic field near the surface of the atomic nucleus. See footnote (1) to learn about Tesla. This magnetic field is so strong that if the magnet was 100,000 miles away it would still rip a kitchen knife out of your hand. Forget about the credit cards in your pocket, they’re history.
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-------------- Pulsar --------------------- 100,000,000 Tesla
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Largest permanent magnet ---------------- 30
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Surface of Sun ---------------------------- .02
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Refrigerator magnet ---------------------- .02
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Surface of Earth--------------------------- .00005
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Human Body ------------------------------- .0000000003
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Interstellar galactic space ----------------- .000000000002 Tesla
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- How is this enormous magnetic field created in the Magnetar neutron star? How does a spinning neutron star get created? How can supernova stars explode in the first place?
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- Astronomers do not understand how a supernova explosion can happen. If we assume gravitational energy caused by the collapsing star is the potential energy needed to blow the star apart, the math does not work out. The math says the star should collapse back on itself rather than explode.
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- An answer may be coming from automotive engineering. Engineers studying burning gasoline with oxygen have learned that turbulence is a big factor. Engineers find two factors with turbulence, one called detonation and the other called deflagration.
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- These two factors added into computer modeling of supernovas do allow them to explode. Turbulence inside the star causes nuclear burning to occur so fast the star’s gravity has no time to compensate. Turbulence allows kinetic energy to shift from larger scales to smaller scales where thermo nuclear energy becomes concentrated and the explosive energy can not be contained.
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- Magnetic fields play a role in supernova explosions as well. Somehow magnetic fields squeeze matter outward along the rotational axis in two polar jets. It is these rotating jets that create the pulsars.
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- The effect of neutrinos is still another variable. Also the effects of gravitational waves. Not only do collapsing stellar cores produce intense bursts of neutrinos they also shake the fabric of space-time.
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- Still another factor may be the metal richness of the star. Each generation star contains the higher level elements of previous generations of supernova explosions. The metal rich content may change the magnetic properties of the supernova. All of these variables play a part in the properties of a supernova.
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- Magnetars are at an extreme edge of the families of supernova explosions that we observe. About one supernova occurs somewhere in the cosmos each day.
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- Astronomers estimate that there are at least 100 Magnetars in our Milky Way. We have found a dozen so far and 10 years ago we did not know they even existed. There is still a lot to learn.
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------------------------- Footnote:
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(1) The Tesla is a unit of magnetic flux. It is 1 kilogram / coulomb* second. Or, in other units it is 1 kilogram/ampere*second^2. 1 Tesla - 10,000 gauss.
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- The unit is named after Nikola Tesla a Croatian American (1856 - 1943). Edison went back on a promise to pay Tesla for one of his inventions. So, Tesla went in business for himself.
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- He worked out how to use AC current through transformers to increase voltage in transmission lines to allow electricity to be sent over long distances with minimum power loss. Then, drop the voltage back down at the receiving end with another transformer for household use.
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- Tesla invented motors that work on alternating current. Everyone else at the time was working with direct current electricity ( including Edison).
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--------------------------------- Other Reviews available:
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- 2726 - MAGNETISM - throughout the Universe? In astronomy there are more distant, cosmic magnetic fields that are the reason that pulsars act like radio lighthouses and vast clouds of electrically conducting gas get sculpted into strange and unusual shapes.
- 2600 - MAGNETARS - magnetic stars? Magnetism is one manifestation of the electromagnetic force, which is one of the four forces known in the universe. All material that we know of is magnetic at some level. The electrons spin about the atom and the electrons themselves spin so that each atom becomes a tiny atomic magnet. To go from the smallest to the very largest magnetic fields we need to go from atoms to stars.
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- 2341 - Magnetism is one manifestation of the electromagnetic force, which is one of the four forces known in the universe. All material that we know of is magnetic at some level. The electrons spin about the atom and the electrons themselves spin so that each atom becomes a tiny atomic magnet. To go from the smallest to the very largest magnetic fields we need to go from atoms to stars.
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- 2154 - Magnetism is a force that exerts attractive or repulsive force on other materials. All materials are influenced to a greater or lesser degree by the presence of a magnetic field. All materials! Magnets come in two basic types, permanent magnets and electromagnets. Magnetism is ultimately the result of movement of an electric charge. The most common use of Nuclear Magnetic Resonance is in medicine.
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- 1878 - Magnetic structures in the Galaxies. New mysteries are uncovered to understand how magnetic fields throughout galaxies affect star formation and galactic structure. New tools are creating 3-D maps. Dark Matter remains 85% of the undiscovered.
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- 1383 - Magnetars are lethal Neutron Stars. Neutron Stars are exceedingly dense. They have a ½ mile thick indestructible crust floating on a fluid of subatomic particles. The fluid is a plasma of neutrons, protons, and electrons that are no longer atoms. The core is made of neutrons which is the remnant of a massive star that exploded as a supernova. The Neutron Star is what was left behind. The rest blew into outer space.
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- 1223 - Where do big stars go when they die? Big stars have short lives and dramatic deaths. This review highlights the bigger supernovae explosions that create Gamma Ray Bursts, Magnetars, and Pulsars. It refers to a small satellite student project that hopes to contribute to our understanding of these cosmic wonders.
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- 1159 - What are Magnetars? After a supernova explosion of a massive star the remaining core can collapse into a Neutron Star, or a Blackhole, depending on how massive the core is that remains. In certain situations the core could be a rapidly spinning , intensely magnetic Neutron Star, called a Magnetar. Neutron Stars are made of neutrons, not charged particles. Spinning neutrons would not create a magnetic field. Nothing escapes a Blackhole. So, how can Neutron Stars and Blackholes create the enormous magnetic fields?
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- May 1, 2020 704 2727
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