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!

Astrophysics - Apparent Magnitude of stars in a close binary system

  1. Jan 26, 2009 #1
    1. The problem statement, all variables and given/known data

    2 solar type stars are in a close binary system. Each indivual star has an apparent brightness of m = 10 mag.

    Determine the apparent magnitudes of the combined system of the 2 stars assuming they cannot be resolved as individual objects. Determine the minimum brightness for this eclipsing binary when 100%, 75%, 50% and 25% of the stellar survace are covered during the eclipse.

    2. Relevant equations

    m1 - m2 = -2.5 log(f1/f2)

    3. The attempt at a solution

    m1 - m2 = -2.5 log (f1/f2)
    10-10 = -2.5log(f1/f2)
    f1/f2 =1

    m1+2 - m2 = -2.5 log (f1+f2 \ f2) f1 = f2
    m1+2 - m2 = -2.5 log (2f1 \ f1)
    m1+2 - m2 = -2.5 log 2
    m1+2 = -2.5log2 + 5 mag
    m1+2 = 4.25 mag

    Then I'm not sure how to continue from here - any help would be most appreciated!
  2. jcsd
  3. Jan 26, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    One magnitude represents a change in brightness of a factor of around 2.5
    so if you double the brightness (ie two stars) the apparent mag of the combination is only going to change by less than 1mag
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Astrophysics - Apparent Magnitude of stars in a close binary system
  1. Binary Star System (Replies: 11)

  2. Binary star systems (Replies: 6)

  3. Binary star systems (Replies: 1)