1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Difference in Magnitudes

  1. Dec 9, 2006 #1
    1. The problem statement, all variables and given/known data
    One star is intrinsically 100 times brighter than the other. If the brighter star is twice as far away as the dimmer star, what is the difference in their m values and their M values.

    2. Relevant equations
    None were given.

    3. The attempt at a solution
    The equation I've been using most frequently in this problem set is M + m = 5 - 5logd, but I'm not really sure how or even if I can apply it here, since this problem is reverse of what I've been given so far. Usually I have magnitudes and am asked to find the distance.

    Any help you can offer will be greatly appreciated. :smile:
  2. jcsd
  3. Dec 9, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The difference in magnitude between two stars given their brightness is thus:

    [tex] m_2-m_1=2.5 \log(\frac{b_1}{b_2}) [/tex]

    This relates to apparent brightness and apparent magnitude.
  4. Dec 9, 2006 #3
    Thanks for your help!!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?