Sunday, November 22, 2020

MAGNETIC FIELDS - they get big in astronomy?

 -  2912  -MAGNETIC  FIELDS  -  they get big in astronomy?   Magnets get really powerful in astronomy.   Astronomers have measured a 1,000,000,000 Tesla Magnetic Field on the Surface of a Neutron Star.  It is the strongest magnetic field ever recorded in the Universe. The record-breaking field was discovered at the surface of a neutron star called GRO J1008-57 with a magnetic field strength of approximately 1 BILLION Tesla. 


---------------------  2912  -   MAGNETIC  FIELDS  -  they get big in astronomy?

-   For comparison, the Earth’s magnetic field clocks in at about 1/20,000 of a Tesla, tens of trillions of times weaker than you’d experience on this neutron star…and that is a good thing for your general health and wellbeing.

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-  Neutron stars are the “dead cores” of once massive stars which have ended their lives as supernova. These stars exhausted their supply of hydrogen fuel in their core and a power balance between the internal energy of the star surging outward, and the star’s own massive gravity crushing inward, is cataclysmically unbalanced.  

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-  Gravity wins. The star collapses in on itself. The outer layers fall onto the core crushing it into the densest object we know of in the Universe.  It becomes a neutron star. Even atoms are crushed. Negatively charged electrons are forced into the atomic nuclei meeting their positive proton counterparts creating more neutrons. 

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-  When the star’s core can be crushed no further, the outer remaining material of the star rebounds back into space in a massive explosion,  It explodes as a a supernova. The resulting neutron star, made of the crushed stellar core, is so dense that a single sugar-cube-sized sampling would weigh billions of tons, as much as a mountain. Neutron stars are typically about 20 kilometers in diameter and can still be a million degrees Kelvin at the surface.

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-  But if they’re “dead  stars,” how can neutron stars be some of the most magnetic and powerful objects in the Universe?  GRO J1008-57 is a spinning neutron star or “pulsar.” 

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-  Pulsars were first discovered in 1967 by Jocelyn Bell through observations of a regular radio “pulse” of 1.33 seconds.  The pulses were determined not to be of human origin so the object was designated LGM1 (Little Green Men 1). 

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-  A spinning neutron star projects a beam of energy along its magnetic poles that sweeps across space as the star rotates, like the beams from a turning lighthouse. Depending on the orientation of the star, those beams can sweep along Earth’s field of view resulting in a “pulse” of energy with each of the star’s rotations.

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-   But why do neutron stars have incredibly powerful magnetic fields? Seems counterintuitive given that they are made of neutrally charged particles, where neutron gets its name. If you were to cut away a neutron star, it is formed of several layers. A cloud of remaining electrons near the surface, further down traces of charged “impurities” of various atomic nuclei remaining after the formation of the neutron star, a crust of neutrons, and a core of a theorized frictionless neutron fluid further mixed with impurities. 

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-  The combination of layers makes the star incredibly conductive. Spin a very conductive object and you create a churning flow of charged particles which generates a powerful magnetic field. 

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-  Our planet’s own magnetic field is itself created by the rotation of the Earth’s nickel-iron core. However, neutron star rotations are astonishingly fast. Like a figure skater retracting their arms to spin more quickly, the “angular momentum” of the original giant star, millions of kilomtetres in radius, is preserved and transferred to an ever faster spinning compact object only 10 km wide (imagine a spinning figure skater with arms millions of kilometres long pulling them all the way to the centre of their body).

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-   The first neutron star discovered had a rotation period of 1.33 seconds. GRO J1008-57 is 93.3s. Some rotate in mere milliseconds. So, these “dead” stars are the size of a city, denser than any material in the universe, are a million degrees, and spin at a good fraction of the speed of light. 

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-  The rotation of a pulsar is seen from Earth similar to how we see light from a lighthouse at night.  But how can we measure the strength of a pulsar’s magnetic energy? A special technique can be used with a specific class of pulsars which GRO J1008-57 belongs to called accretion powered X-Ray pulsars.

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-  GRO J1008-57 is about 20,000 light years from Earth and is actually in a binary gravitational relationship with a living class B companion star. B’s are hefty stars, a dozen or so times the mass of our Sun and thousands of times brighter. 

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-  GRO J1008-57’s super density creates a powerful gravitational pull 100 billion times more powerful than Earth’s which rips stellar material off its companion. That material falls toward the neutron star. It becomes entangled in the neutron star’s magnetic field flowing along the “lines” of that field to the north and south magnetic poles where it accumulates or accretes on the surface.

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-  The stellar material slams into the surface at half the speed of light releasing tremendous X-Ray energy.  These X-Rays, before radiating away from the neutron star, pass through the magnetic field at the neutron star’s surface. The magnetic field scatters some of the X-Rays leaving a gap or “absorption line” in the spectrum of the X-Rays.

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-   The result is like a fingerprint left by the magnetic field on the X-Ray energy that we can see with our telescopes. Where that absorption line appears along the X-Ray spectrum directly relates to the strength of the magnetic field at the neutron star’s surface where the stellar material is falling. The line phenomenon is known as a “Cyclotron Resonance Scattering Feature“.

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-  In 2017, the brightest X-Ray outburst ever observed from GRO J1008-57 was recorded as spectral lines in the spectrum corresponding to a 1-billion Tesla magnetic field, the most powerful ever recorded in the Universe. Powerful enough to literally pull atoms apart.

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-   A tiny line reveals a distant part of the Universe that we may not be able to “see” but can deduce through decades of research, and our imagination, transforming data into accretion disks, giant stars, plasma flying at near light-speeds, powerful X-Rays, and spinning stellar relics. SCIENCE is amazing!  Other reviews you may e interested in:

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-   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. 

-  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

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-   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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- 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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-  1600 – William Gilbert, the first person to investigate magnetism using scientific methods, publishes  his work in a volume titled “De Magnete“.

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-  1865 – Physics Professor James Clerk Maxwell publishes a paper in which he unifies the areas of electricity and magnetism into a single theory.

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-  1901 – Norway’s Kristian Birkeland  begins building “Terrellas” (little Earths) to test his theory that the aurora are formed by electrons hitting Earth’s magnetic poles.

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-  1908 – American astronomer George Ellery Hale discovers magnetism on the Sun, providing the first evidence of magnetic fields beyond the Earth.

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-  1942 – Swedish physicist Hannes Alfvén theories that when a magnetic field threads through an electrically conducting gas, they become inseparable.

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-  2012 – After 35 years traveling through space, the Voyager 1 spacecraft finally exits the Solar System as it leaves the Sun’s vast bubble of magnetism behind.

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-  November 22, 2020       MAGNETIC  FIELDS                           2912                                                                                                                                                   

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 ---------------------   Sunday, November 22, 2020  -------------------------

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