Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Likelihood of light being absorbed/re-emitted in 50 light years

  1. Jun 26, 2010 #1
    What's the likelihood of light striking some interstellar gas and being absorbed, then re-emitted, and the re-emitted light actually being the light we see rather than the original light from the source? Also, what about the likelihood of reemission after passing through the heliosphere? Anyone care to make a rough guess at the percentage of light that reaches us that is not filtered this way? Are there any particular wavelengths of light that might be more likely to make it through because they aren't likely to be absorbed by the interstellar medium or the heliosphere?
  2. jcsd
  3. Jun 26, 2010 #2
    Hmm, apparently this paper http://www.ekkehard-friebe.de/Brecher-K-1977.pdf answers that question. It says high energy x-rays are less likely to be disturbed... any thoughts? Would high energy x-rays be able to pass through the heliosphere unaffected?
  4. Jun 26, 2010 #3
    When light is absorbed and then re-emitted it is so in random directions isn't it?
  5. Jun 26, 2010 #4
    Apparently hard x rays are absorbed rather well by the earth's atmosphere, so I'm not sure why the 1977 paper does not think the heliosphere would have a similar effect. Can someone help clarify?
  6. Jun 26, 2010 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Pretty likely, we can see the adsorption bands in spectorgraphs of distant objects. Since such adsorpton is usually wavelenght depentent not all of the light is adsorbed. That which does leaves dark bands in the spectrum.
  7. Jun 26, 2010 #6


    User Avatar
    Science Advisor

    You can think of light propagation as vacuum absorbing and re-emitting it. If something else gets in the way and does the same thing, all it's going to change is index of refraction. The light isn't any more "second hand" because of it.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook