Thursday, November 1, 2018

Supernovae from blue, supergiant stars.



-  2149  -  Supernovae from blue, supergiant stars.  At the ends of their lives, blue supergiant stars, which can be over 50 times the mass of the Sun, may collapse to form remnants partly comprising a sea of free quarks and gluons. The conversion of neutrons and other baryons to a quark-gluon plasma in blue supergiant stars could lead to these type supernovae explosions.   
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-  Supernova 1987 ...............  ^^^^^^^^^^^^^^^
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----------------------------------  2149   -  Supernovae from blue, supergiant stars.
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--  Earlier Reviews about supernovae.  More are listed at the end.  This Review 2149 that follows  is a most recent study:
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-  1932  -  Supernova 1987 was a blue super giant supernova that lit up the southern sky.  Even today we are still learning what happened. 
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-  1881  -  Supernovae are like snowflakes, no two are alike.  That gold ring on your finger came from one of these explosions.
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-  1699  Supernovae close to home.  A 20 Solar Mass Red supergiant star could be the next star to blow.  Betelgeuse is only 640 lightyears away.  
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-   1698  -  We are made of elements created in exploding stars.  How rare are we in the Universe? 
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-  1684  -  What does a supernovae explosion sound like?  99% of a supernovas explosion escapes in the form of ejected neutrinos.  The "sound of such an event can last over 1,300 days from ultraviolet, optical, near-infrared, X-rays into a musical tone lasting only a few minutes.
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-  2149  -  At the ends of their lives, blue supergiant stars, which can be over 50 times the mass of the Sun, may collapse to form remnants partly comprising a sea of free quarks and gluons. The conversion of neutrons and other baryons to a quark-gluon plasma in blue supergiant stars could lead to these type supernovae explosions..
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-  These events, which would emit two powerful neutrino pulses in rapid succession, could help to explain how such stars can undergo supernovae explosions.
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-  When stars heavier than about nine solar masses have exhausted all the hydrogen in their cores, they continue fusing helium into carbon and oxygen. They then fuse a series of ever heavier elements, ending with the fusion of silicon into nickel, which decays into iron.
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-   When we reach the element iron the process stalls because no energy can be released by fusing iron nuclei. When the mass of the inert iron core exceeds the Chandrasekhar limit of 1.44 solar masses, it can no longer support itself against its own gravity. The nuclei are crushed and a flood of neutrinos are emitted in a few milliseconds, heating the outer layers that are blown away in a giant supernova explosion.
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-  What happens next is less predictable. The remnants of stars just above the nine-solar-mass limit form neutron stars. In stars above about 70 solar masses, however, this neutrino heating mechanism is not efficient enough to cause a sufficiently-strong explosion for the outer layers to escape the gravitational potential well of the core. The ejected material therefore falls back in and a black hole is formed. In between these limits the details as to what happens are unclear.
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-  If the material ejected by the neutrino heating mechanism collapsed back onto the core, the rise in density could cause the  neutrons at the center of the core to be crushed. As the strong nuclear force becomes weaker at shorter distances, the quarks that make up the neutrons would no longer be bound into individual baryons. Instead quarks would move around freely in a quark-gluon plasma.
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-  The energy released by such a phase transition could re-ignite as a supernova, blowing off the outer layers and producing a neutron star that would stop any further collapse.
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-   However, the equation of state for the quark-gluon plasma used in the 2009 study predicted neutron stars heavier than about 1.6 solar masses should collapse into black holes.  Since then, astronomers have observed two neutron stars with about 2 solar masses.   That means this predicted equation of state was not correct
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-  Armed with a more sophisticated model of the quark-gluon plasma and greater computing power, researchers have now produced a more detailed model of a two-stage supernova in a star of 50 solar masses.
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-  Having initially undergone core collapse, the star undergoes a phase transition into a proto-neutron star, producing a strong pulse of neutrinos. Within a few hundred milliseconds, it has expanded its diameter tenfold and begun to collapse again.
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-  As the shock front propagates inwards, the pressure rises at its center, and almost immediately the center begins to undergo a second phase transition to a quark-gluon plasma. This releases more energy and triggers a second, more powerful shock front propagating outwards.
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-  This stops the inward-propagating rebound from the first shock at a radius of about 50 miles just 1.2 seconds after the initial blast. The supernova then expands to several thousand miles in radius within a few milliseconds. The remnant is a neutron star of about two solar mass with a quark-gluon plasma core.
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-   From the first shock we have a neutrino signal and then, from the conversion to quark matter, we have an antineutrino signal.  Modern neutrino detectors such as Super-Kamiokande in Japan have millisecond time resolution. Therefore, if such a supernova occurred in our galaxy, the presence of two sharp signals barely a second apart, one of neutrinos and one of antineutrinos, should be detectable.
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-  Any signals from extra-galactic events would be diluted so much that they are not detectable. We need a supernova inside our galaxy.  We have to wait to see whether one can see such a supernova explosion with two neutrino bursts.”
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-  Here are other Reviews available about supernovae explosions.:
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-  1932  -  Supernova 1987 was a blue super giant supernova that lit up the southern sky.  Even today we are still learning what happened. 
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-  1881  -  Supernovae are like snowflakes, no two are alike.  That gold ring on your finger came from one of these explosions.
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-  1699 -  Supernovae close to home.  A 20 Solar Mass Red supergiant star could be the next star to blow.  Betelgeuse is only 640 lightyears away.  
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-  1698  -  We are made of elements created in exploding stars.  How rare are we in the Universe? 
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-  1684  -  What does a supernovae explosion sound like?  99% of a supernovas explosion escapes in the form of ejected neutrinos.  The "sound" of such an event can last over 1,300 days from ultraviolet, optical, near-infrared, X-rays into a musical tone lasting only a few minutes.
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-  1566  -  Supernovae are what we are made of.  We are living in and are made of star dust and gas. 
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-  1411  -   What causes supernovae explosions?  The single White Dwarf star is the dead star left over from the explosion.  The hot star will take billions of years to cool down. 
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-  1320  -  Supernova Sn1006 was visible during the day even though it was 7,000 lightyears away. 
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-  1319  -  Supernova 185A.D. is one of about 8 supernovae explosions witnessed by the naked eye in recorded history.  The Chinese recorded this one in 185 A.D. 
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-  1308  -   The Tyco Supernova exploded 400 years ago.  It was first seen in 1572.
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-  984  -  The art of astronomy. 
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-  929  -    The youngest supernova. 
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-  831  -  Supernova 1987A first seen February 23 , 1987.
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-  613  -  From supernova to our Sun.
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-  579  -  Exploding stars create life, destroy life. 
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-  510  -  Supernova you can see.
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-  508  -  You are made of star dust.
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-  504  -  Accelerating universe from unknown force.
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-  508  -  Supernova start out as a giant gas nebula that gradually takes shape due to gravity .  The lives of these stars are controlled by their initial mass. 
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-  5  -  Cosmos, everything but quiet.
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-  November 1, 2018.      
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 ---------------------   Thursday, November 01, 2018         -------------------------
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