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Neutrinos from the main fusion reaction which powers the sun.

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  • Neutrinos from the main fusion reaction which powers the sun.

    At long last, neutrinos from the main (proton-proton) fusion reaction which powers the sun, have been detected.


    Neutrinos from the primary proton–proton fusion process in the Sun

    Originally posted by abstract, link above
    In the core of the Sun, energy is released through sequences of nuclear reactions that convert hydrogen into helium. The primary reaction is thought to be the fusion of two protons with the emission of a low-energy neutrino. These so-called pp neutrinos constitute nearly the entirety of the solar neutrino flux, vastly outnumbering those emitted in the reactions that follow. Although solar neutrinos from secondary processes have been observed, proving the nuclear origin of the Sun’s energy and contributing to the discovery of neutrino oscillations, those from proton–proton fusion have hitherto eluded direct detection. Here we report spectral observations of pp neutrinos, demonstrating that about 99 per cent of the power of the Sun, 3.84×10[sup]33[sup] ergs per second, is generated by the proton–proton fusion process.

    Sci Am write up is here:-

    http://www.scientificamerican.com/ar...cted-borexino/

  • #2
    Originally posted by rwatts View Post
    At long last, neutrinos from the main (proton-proton) fusion reaction which powers the sun, have been detected.


    Neutrinos from the primary proton–proton fusion process in the Sun




    Sci Am write up is here:-

    http://www.scientificamerican.com/ar...cted-borexino/

    A bit of background for those who may not be aware of the importance of this.

    It's been the case since the mid 20th century, that fusion reactions between protons likely power the sun. Deep in its core where temperatures are in the tens of millions of degrees centigrade, proton speeds are so high that protons smash into each other and fuse, forming helium nuclei as a kind of chemical ash. In the process of this fusion, a small amount of energy is released, but given the zillions of ions (in this case, hydrogen atoms missing their orbiting electrons) in the sun's core, each small bit of liberated energy adds up to a massive amount, and so we end up with a very hot star.

    That's been the theory and it's been a very successful one with a lot of supporting, but indirect evidence.

    If fusion reactions really were occurring, then a by-product of these reactions were expected to be utterly small, almost massless particles called neutrinos. Given their smallness and near masslessness (?), neutrinos could easily escape the core of the sun and hence be detected.

    Experiments were begun in the 1960s to detect these neutrinos. And they were, but only about a third of the expected number. This was a problem that lasted for decades, solved only when scientists discovered that neutrinos could actually change their type between two other versions of the particle. This "neutrino oscillation" solved the "solar neutrino problem".

    However, these neutrinos were from a fusion side reaction, not the main reaction itself.

    In 1987, more excitement occurred when the supernova 1987A was detected in one of the Magellanic Clouds. Three or four neutrinos were detected which likely came from that explosion. However, those neutrinos were from an exploding star.


    The report I provide here concerns itself with the first detection of neutrinos which result from the main energy generating fusion reactions in the sun's core.

    It's not actually directly seeing those fusion reactions. But it is observations of an expected by-product and so is further evidence that we really do understand something about what powers the stars.
    Last edited by rwatts; 08-28-2014, 06:10 PM.

    Comment


    • #3
      Originally posted by rwatts View Post
      It's not actually directly seeing those fusion reactions. But it is observations of an expected by-product and so is further evidence that we really do understand something about what powers the stars.
      But detecting those neutrinos is fundamentally not different from detecting photons with one's eyes. Photons generated in the solar core might eventually emerge from the surface of the sun, though I would concede it's exceedingly unlikely.
      The greater number of laws . . . , the more thieves . . . there will be. ---- Lao-Tzu

      [T]he truth I’m after and the truth never harmed anyone. What harms us is to persist in self-deceit and ignorance -— Marcus Aurelius, Meditations

      Comment


      • #4
        Originally posted by Truthseeker View Post
        But detecting those neutrinos is fundamentally not different from detecting photons with one's eyes. Photons generated in the solar core might eventually emerge from the surface of the sun, though I would concede it's exceedingly unlikely.
        They do, it takes several thousand years for a gamma ray photon emmitted in the core, to escape through the suns surface. By that time it would have cooled and been scattered so much that no information can be derived about what's inside the core, merely from detecting the photon.

        Its only with neutrino detectors that we get to take a direct peak at the core. Otherwise we're limited to comparing theoretical models of how the exterior of the sun should behave given a core of such and such properties.

        Comment


        • #5
          Originally posted by Truthseeker View Post
          But detecting those neutrinos is fundamentally not different from detecting photons with one's eyes. Photons generated in the solar core might eventually emerge from the surface of the sun, though I would concede it's exceedingly unlikely.
          AFAIK it takes a core gamma photon on the order of a million years to emerge from the photosphere.

          Also, neutrinos are MUCH more difficult to detect than photons.

          K54

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