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Calculating distance to a star using magnitudes

  1. Sep 26, 2016 #1
    1. The problem statement, all variables and given/known data
    Obs.JPG

    2. Relevant equations
    ##m = m_0 − 2.5 log_{10} f## where ##m## is the absolute magnitude of an object, and ##m_0## is the zero point.

    3. The attempt at a solution

    I'm having difficulty with is part b, the answer to which I believe is required for the subsequent parts.

    I obtain the following through treatment of the given equation: ##M_{abs}=m_{obs}-5log_5(\frac{d}{10})## where ##d## is the distance we're looking to compute. Using the fact that both Star A and Vega are A0 stars, I assumed that the absolute V-band magnitude of Star A would be the same as Vega's, which would be ##M_{abs}=+0.6##, however the observed/apparent magnitude ##m_{obs}## remains unknown, and so I'm unable to proceed to compute the distance.

    It seems simple, but I can't quite put my finger on it..
     
  2. jcsd
  3. Sep 27, 2016 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    You'll need the R-band magnitude of Vega I think. The question part about the colors indicates that you have to find some relation between R and V band.
    Afterwards you can use the R band magnitude from (a).
     
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