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Cosmic rays

  1. May 19, 2006 #1
    I read an article in this months Discover magazine that stated that cosmic rays are atoms of the elements from hydrogen up to iron traveling at close to the speed of light that originate from exploding stars. Can the mass of cosmic rays be calculated for the universe? Is it a constant? As some rays are absorbed new ones are formed but is it generally uniform?

  2. jcsd
  3. May 19, 2006 #2
    Sounds like crackpot science to me.

    Cosmic Rays is not a sole "thing". It is radiation consisting of high-energy particles (protons, alpha particles are the most common ones). Atomic nuclei, electrons and gamma rays and high-energy neutrinos is also included.

    Futhermore, there are more sources of cosmic rays that just supernovae. I do not know if it possible to somehow measure or calulate the total mass of all the cosmic rays in the universe.
  4. May 19, 2006 #3
    Perhaps they were only describing certain aspects of cosmic rays. The artical was all about how we won't be able to travel to other planets unless we can eliminate the affects of cosmic rays on the human body.

  5. May 19, 2006 #4


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    There is what is known as "Galactic Cosmic Radiation", which is much the same as the solar wind (high energy atoms, ions and electrons) from our own sun, but comes from all other sources in the galaxy, and perhaps other galaxies.

    See -



    [url]http://hesperia.gsfc.nasa.gov/sspvse/oral/Ken_McCracken/wintergreen1.pdf[/url] (use save target as)


    [url=http://www.nature.com/nature/journal/v255/n5511/abs/255687a0.html;jsessionid=D3C86159CC3D1A72216F9744FB4527D1]Anisotropy of cosmic radiation in the Galaxy[/url]

    There exists an spectrum of energy of Galactic Cosmic Radiation, with the higher energies >> being relatively rare.

    Particles with energy as high as 10[sup]20[/sup] eV have been reported, and these are certainly near the speed of light. Consider that a single nucleon (proton or neutron) has rest mass slight less than 0.940 GeV.
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  6. May 20, 2006 #5


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    Our theories of cosmic ray acceleration are a bit fuzzy, so I don't think one could do a very accurate estimate of the overall mass of cosmic rays in the universe, but the total mass would be very, very small. The energy density, on the other hand, is about an eV per cubic centimeter in the Milky Way. This is comparable to the local energy density of the cosmic microwave background, starlight, and magnetic fields, but negligible compared to the critical density.

    No, if they are reallly accelerated in supernovae or gamma-ray bursts, then their density should be changing along with the star formation rate density (which has been decreasing since z~2).

    No, the density of cosmic rays should be greatly enhanced near galaxies and clusters. Large-scale magnetic fields in the host galaxies will trap many of the charged cosmic rays.
  7. May 23, 2006 #6


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    If you go down to more local levels, you will probably find some other extreme variations.

    For example, along the beams from GRBs, and (especially) in and along jets, from quasars and AGNs, as well as micro-quasars (this is in addition to the environs of supernovae and their remnants, as has already been pointed out).
  8. May 24, 2006 #7
    Thanks guys.
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