Thursday, January 5, 2023

3809 - MAGNETIC STAR - X-ray telescopes new discoveries?

 

      3809  -   MAGNETIC  STAR  -     X-ray telescopes new discoveries?  Launched on December 9, 2021, IXPE is the first satellite that can measure the polarization of X-ray light with this level of sensitivity and clarity. It was designed to discover the secrets of some of the most extreme objects in the universe the remnants of supernova explosions, powerful particle streams spit out by feeding black holes.

          


            ---------  3809  -  MAGNETIC  STAR  -        X-ray telescopes new discoveries?

            -   The X-ray light emitted by a certain “magnetar”, a highly magnetized dead star, indicates that this star has a solid surface and no atmosphere.

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            -   The “Imaging X-ray Polarimetry Explorer” (IXPE) satellite reveals that a highly magnetized dead star known as a magnetar has a solid surface with no atmosphere.  This represents the first time polarized X-ray light from a magnetar has been observed.

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            -        “IXPE” allows scientists to examine X-ray light in space by measuring its polarization, the direction of the light waves’ oscillation. The magnetar        “4U 0142+61”, located in the Cassiopeia constellation is 13,000 light years from Earth.

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            -        Magnetars are neutron stars which are very dense remnant cores of massive stars that have exploded as supernovae at the ends of their lives. Unlike other neutron stars, they have an immense magnetic field, the most powerful in the universe.

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            -    Magnetars emit bright X-rays and show erratic periods of activity, with the emission of bursts and flares which can release in just one second an amount of energy millions of times greater than our Sun emits in one year. They are believed to be powered by their ultra-powerful magnetic fields, 100 to 1,000 times stronger than standard neutron stars.

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            -        They found a much lower proportion of polarized light than would be expected if the X-rays passed through an atmosphere.  Polarized light is light where the wiggle is all in the same direction, the electric fields vibrate only in one way. An atmosphere acts as a filter, selecting only one polarization state of the light.

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            -        The team also found that for particles of light at higher energies, the angle of polarization, flipped by exactly 90 degrees compared to light at lower energies, following what theoretical models would predict if the star had a solid crust surrounded by an external magnetosphere filled with electric currents.

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            -   But, like with water, temperature is also a factor, a hotter gas will require a stronger magnetic field to become solid.  The most exciting feature they could observe is the change in polarization direction with energy, with the polarization angle swinging by exactly 90 degrees.

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            -        Quantum theory predicts that light propagating in a strongly magnetized environment is polarized in two directions, parallel and perpendicular to the magnetic field. The amount and direction of the observed polarization bear the imprint of the magnetic field structure and of the physical state of matter in the vicinity of the neutron star.

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            -        At high energies, photons (particles of light) polarized perpendicularly to the magnetic field are expected to dominate, resulting in the observed 90-degree polarization swing.

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            -        The polarization at low energies is telling us that the magnetic field is likely so strong to turn the atmosphere around the star into a solid or a liquid, a phenomenon known as “magnetic condensation”.

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            -        The solid crust of the star is thought to be composed of a lattice of ions, held together by the magnetic field. The atoms would not be spherical but elongated in the direction of the magnetic field.

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            -        It is still a subject of debate whether or not magnetars and other neutron stars have atmosphere. 

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            -        The “Imaging X-ray Polarimetry Explorer” has measured and mapped polarized X-rays from the remains of this exploded star. The findings come from observations of Cassiopeia A, a famous stellar remnant. The results shed new light on the nature of young supernova remnants, which accelerate particles close to the speed of light.

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            -        All forms of light, from radio waves to gamma rays, can be polarized. Unlike the polarized sunglasses we use to cut the glare from sunlight bouncing off a wet road or windshield, IXPE’s detectors map the tracks of incoming X-ray light. Scientists can use these individual track records to figure out the polarization, which tells the story of what the X-rays went through.

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            -        Cassiopeia A was the first object IXPE observed after it began collecting data. One of the reasons “Cas A” was selected is that its shock waves, like a sonic boom generated by a jet, are some of the fastest in the Milky Way. The shock waves were generated by the supernova explosion that destroyed a massive star after it collapsed. Light from the blast swept past Earth more than three hundred years ago.

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            -        Magnetic fields, which are invisible, push and pull on moving charged particles like protons and electrons.   In an exploding star, magnetic fields can boost these particles to near-light-speed.

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            -        Despite their super-fast speeds, particles swept up by shock waves in Cas A do not fly away from the supernova remnant because they are trapped by magnetic fields in the wake of the shocks. The particles are forced to spiral around the magnetic field lines, and the electrons give off an intense kind of light called “synchrotron radiation,” which is polarized.

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            -        By studying the polarization of this light, scientists can “reverse engineer” what’s happening inside Cas A at very small scales, The angle of polarization tells us about the direction of these magnetic fields. If the magnetic fields close to the shock fronts are very tangled, the chaotic mix of radiation from regions with different magnetic field directions will give off a smaller amount of polarization.

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            -    Previous studies of Cas A with radio telescopes have shown that the radio synchrotron radiation is produced in regions across almost the entire supernova remnant. Astronomers found that only a small amount of the radio waves were polarized, about 5%. They also determined that the magnetic field is oriented radially, like the spokes of a wheel, spreading out from near the center of the remnant towards the edge.

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            -        Data from NASA’s Chandra X-ray Observatory, on the other hand, show that the X-ray synchrotron radiation mainly comes from thin regions along the shocks, near the circular outer rim of the remnant, where the magnetic fields were predicted to align with the shocks.

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            -   Chandra and IXPE use different kinds of detectors and have different levels of angular resolution, or sharpness. Launched in 1999, Chandra’s first science image was also of Cas A.

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            -        Cassiopeia A is the remnant of a supernova explosion that appeared in our sky more than 300 years ago. It is located a distance of approximately 11,000 light years from Earth. Its name is taken from the constellation in which it is seen, Cassiopeia, the Queen.

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            -    A supernova is the cataclysmic explosion that occurs at the end of a massive star’s life. Cas A is the expanding shell of material that remains from such an explosion.

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            January 1, 2022                            3804                                                                                                                              

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