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Red shift question

  1. Oct 24, 2007 #1
    Hello friends!!!

    Would a star (O-Type) with max output peaking in the UV range, which was subject to (at distance) redshift 8 end up in the IR spectrum when its light approached earth? Would this be taking into consideration the doppler effect?

    BTW, yes this is somewhat an extension of my previous question but Im also working on it! another few hours of searching hes led to its evolution to this question. Im just trying to figure out the effect of distance (space) on a light source given the applicable laws (obviously dopplers law here) I think a stars red shift would work well!!

    Thanks!!
     
    Last edited: Oct 24, 2007
  2. jcsd
  3. Oct 26, 2007 #2
    Well, the level of redshift depends on the relative velocity between the star and Earth.
    If the star was moving fast enough away from Earth it should be theorethically possible to have a great shift in the observed spectrum of the star, though I am unsure of the greatest shift measured so far. Also, when considering redshift one must also take into account the time period over which it is measured.

    Redshift is all about the doppler effect yes. But the light from the star does not change "as its light approaches earth". Remember that it is the frequency and the wavelength that changes, but energy of the photon remains the same.
     
  4. Oct 26, 2007 #3
    I don't think so. If there is a star moving away from Earth very fast (let say half c) , and the star illuminates a very narrow band of light at certain frequency and at pulses. Then from Earth we can detect the light from the star at lower frequency, meaning lower energy. The trick here is that we can receive longer pulses.
     
  5. Oct 26, 2007 #4
    That is true yes. But a lower frequency does not mean lower energy as the wavelength is increased. E=fw
    You could be right, still. I'll do some research on this and get back to you;)

    However, I feel I expressed myself a bit cryptically and do appologize for this. The intention was that it is the intensity of the light that decreases as the relative velocity increases.
     
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