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Homework Help: Speed of galaxies by redshift

  1. Apr 18, 2010 #1
    1. The problem statement, all variables and given/known data
    I am trying to calculate, from their redshifts, the speed at which each of the following galaxies is moving away from us. Give your answers in both km/s and as a fraction of the speed of light.

    The galaxies are:
    Galaxy 1: Observed wavelength of hydrogen line is 659.2 {\rm nanometers}.
    Galaxy 2: Observed wavelength of hydrogen line is 664.4 {\rm nanometers}.
    Galaxy 3: Observed wavelength of hydrogen line is 683.1 {\rm nanometers}.

    Additional Info:
    Imagine that you have obtained spectra for several galaxies and have measured the observed wavelength of a hydrogen emission line that has a rest wavelength of 656.3 nanometers. The above galaxies are the results.
     
  2. jcsd
  3. Apr 18, 2010 #2
    oops, that should read,
    "Galaxy 1: Observed wavelength of hydrogen line is 659.2 nanometers.
    Galaxy 2: Observed wavelength of hydrogen line is 664.4 nanometers.
    Galaxy 3: Observed wavelength of hydrogen line is 683.1 nanometers. "
     
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