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Homework Help: Change in magnitude and flux caused by a planet transiting a star

  1. Mar 2, 2010 #1
    1. The problem statement, all variables and given/known data

    Determine the dip in magnitudes and flux in the optical light curve caused by the planet in front of the star if the planet orbits at 0.1,1 and 5 AU:
    The star is a solar type star and the mass of both the planet and star are known as are their radii:
    The observer is 10pc away from the star

    2. Relevant equations

    dF/F0 = (rp/rs)2
    rp = planet radius
    rs = star radius

    3. The attempt at a solution
    using this equation the change in flux can be determined however I am unsure if the distance between the star and the planet will have any effect. My initial thought is no considering how much greater 10pc is than 1AU but i'm not confident. But if there is a relation I have been unable to find it. Thank you in advance;
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 2, 2010 #2


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    Homework Helper

    That's correct: because 10pc is so much greater than 1AU, the distance doesn't matter. To show that it doesn't, you can rigorously calculate the angular sizes of both the planet and the star, get the answer that way, and compare to the answer you get by using dF/F0 = (rp/rs)2.
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