- 2815 - WHITE DWARF - spinning neutron star? A White Dwarf star is the left over core of a star that has exploded in a supernova. It has the mass of the Sun and has the volume of the Earth. Therefore it is a very dense material made of neutrons, or electron - degenerate matter. No fusion takes place anymore so it is a “dead star” continuously loosing its thermal energy
-------------------------- 2815 - WHITE DWARF - spinning neutron star?
- White Dwarf leftover cores from sun like stars can live a long time. White Dwarfs can live for trillions of years through the support of exotic quantum physics.
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- Astronomers recently spotted perhaps the strangest exotic white dwarf star to date. This is a dead star the spins twice a second, sucking down material from a nearby companion as it goes around. The Earth takes 86,400 seconds to spin just once. Our star , the Sun, takes 2,073,600 seconds per rotation.
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- When stars like the Sun die, they expand off their outer atmospheres into space. After this explosion dies down, only the core, a white-hot ball of carbon and oxygen, is left behind. That ball, no bigger than planet Earth, is supported not by the normal nuclear fusion like inside living stars, but by the exotic quantum force known as “degeneracy pressure“.
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- Most stars do not live alone; most have siblings. And these stars can orbit their companion and end their life in a blaze, leaving behind the corpse that is a white dwarf. Over time, that companion can either begin the final stages of its life itself, or spiral in enough to begin descending orbits. .
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- When that happens, material from the white dwarf's companion can wind up on the surface of the white dwarf, building a thick layer of hydrogen around its carbon-oxygen core body.
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- In this situation and with enough time and enough material, a cataclysm can occur. That is a flash of nuclear fusion created by the intense pressures in the star’s atmosphere. This flash of energy releases in a blast of radiation, visible from light-years away.
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- These events used to be called "novas," but nowadays astronomers prefer the term "cataclysmic variable star".
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- Astronomers spotted a unique cataclysmic variable star they named J2056. A binary system sitting about 850 light-years away from Earth, J2056 is known as an "intermediate polar" cataclysmic variable star. The complex name is meant to suggest some physics that is also complex.
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- White dwarf neutron stars are full of charged particles. They are also relatively small and spin quickly. The quickly spinning charged particles generate magnetic fields, which fan out far beyond the surface of the white dwarf and affect how the material from its companion star actually makes it onto the surface of the white dwarf.
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- If the white dwarf star's magnetic fields are weak, the hydrogen from its companion star settles into a regular disk of accretion, steadily feeding onto the white dwarf.
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- If the magnetic fields are strong, they funnel the gas into streams that wrap around the white dwarf and strike the poles, like a super-charged aurora borealis, or what we call he “northern lights”
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- If the magnetic fields are not too weak, but not too strong, an "intermediate polar" star is formed. The word "polar" refers to the structure of the magnetic field itself. In this case, the magnetic fields aren't strong enough to completely disrupt the formation of an accretion disk, but they are strong enough to tangle up the gas near the white dwarf. This prevents a regular, smooth flow of gas, causing the white dwarf to flicker and flare irregularly and unpredictably.
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- J2056 is an intermediate polar system, which means that gas from its companion star can form an accretion disk around the white dwarf, but it has trouble actually making it to the white dwarf's surface. This white dwarf is only capable of accumulating about the equivalent of Earth's atmosphere every year.
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- J2056 isn't emitting a lot of X-ray radiation, which is atypical of these kinds of systems.
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- J2056 is spinning fast. In fact, it's the fastest-known confirmed white dwarf, clocking in at a rotation period of roughly 29 seconds per revolution.
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- How did J2056 get so fast? It could be that the configuration of its magnetic fields are just right and therefore able to pull material down onto its surface in quick spurts, accelerating the white dwarf like a stellar carousel.
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- But, its magnetic fields aren't strong enough to slow down the rotation through electromagnetic interactions with the surrounding accretion disk.
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- Still, the relative dimness of its X-rays and the supremely fast orbit of its companion that orbits once every 1.76 hours remain to be explained.
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- J2056 could represent a brand-new class of cataclysmic variable stars, or it could be just a complete oddball. Either way, understanding how it works could help us to understand how magnetic fields operate around white dwarfs, which is important for understanding how they live and how they are born.
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- Stay tuned there is much more to learn. This is a great thing about astronomy.
The more you learn the more you realize you don’t know.
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- September 7, 2020 2815
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