Shedding light on origin of excess anti-matter:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Nov 17, 2017.

  1. paddoboy Valued Senior Member


    High-altitude observatory sheds light on origin of excess anti-matter
    November 16, 2017

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    The HAWC Observatory, perched next to a volcano at an altitude of 13,500 feet, uses its 300 massive water tanks to scoop up the products of high-energy particle collisions happening in the upper atmosphere. Credit: Jordan Goodman
    A mountaintop observatory in Mexico, built and operated by an international team of scientists, has captured the first wide-angle view of gamma rays emanating from two rapidly spinning stars. The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory provided the fresh perspective on high-energy light streaming from these stellar neighbors, casting serious doubt on one possible explanation for a mysterious excess of anti-matter particles near Earth.

    In 2008, astronomers observed an unexpectedly high number of positrons—the anti-matter cousins of electrons—in orbit a few hundred miles above Earth's atmosphere. Ever since, scientists have debated the cause of the anomaly, split over two competing theories of its origin. Some suggested a simple explanation: The extra particles might come from nearby collapsed stars called pulsars, which spin around several times a second and throw off electrons, positrons and other matter with violent force. Others speculated that the extra positrons might come from processes involving dark matter—the invisible but pervasive substance seen so far only through its gravitational pull.

    Read more at:

    the paper:

    Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth:


    The unexpectedly high flux of cosmic-ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the High-Altitude Water Cherenkov Observatory (HAWC), of extended tera–electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera–electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin.

    Exotic origin for cosmic positrons:
    Several cosmic-ray detectors have found more positrons arriving at Earth than expected. Some researchers interpret this as a signature of exotic physics, such as the annihilation of dark matter particles. Others prefer a more mundane explanation that involves positron generation at pulsars followed by diffusion to Earth. Abeysekara et al. detected extended emission of gamma rays around two nearby pulsars, generated by high-energy electrons and positrons. The size of the extended emission was used to calculate how far positrons generated by the pulsars diffuse through space—which turns out to be insufficient to reach Earth. The excess positrons detected on Earth must therefore have a more exotic origin than nearby pulsars.
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  3. mathman Valued Senior Member

    The essential point was that pulsars did not explain the origin of the positrons. Dark matter reaction is a possibility.
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  5. LaurieAG Registered Senior Member

    I heard this on ABC News radio last week and I wondered why the journalists were talking about dark matter when the story was clearly about anti-matter??

    It's in the thread title, the article link below and here's a quote from the article.
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  7. mathman Valued Senior Member

    The anti-matter particles referred to are positrons. The open question is their origin. Dark matter interaction is a possibility.
  8. LaurieAG Registered Senior Member

    As there's no mention of dark matter in the article and the text says "it appears that serious doubt is cast on one possible explanation" is the one possible explanation that is in serious doubt dark matter or are you just speculating?
  9. exchemist Valued Senior Member

    Dark matter is said, by the phys org article, to be one "exotic" possible source of the observed excess of positrons near the Earth.

    The research in question casts serious doubt on one "mundane" alternative explanation for the positrons, namely that they might come from pulsars.

    So, with pulsars out of the picture, science is forced to consider further these "exotic" explanations, I presume.
  10. LaurieAG Registered Senior Member


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