Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Luminosity Equation Question

  1. Dec 25, 2014 #1

    I've been trying to solve for the luminosity of Gliese 581 using its brightness. I've been using the equation below:


    F = (L/(4*pi*r^2))

    I have the flux as the absolute brightness of Gliese 581, which is 11.6. The distance, r, to the star is 1.89210568 × 10^17 meters. However, when I input all of that into the equation, I get 5.21 * 10^36 watts. That does not seem even close to the correct answer, which should be about 6.38 * 10^24 watts. What did I do wrong?
  2. jcsd
  3. Dec 25, 2014 #2
    In which units?
    You need F in units if W/mˇ2
    How do you get that?
    Because that "absolute brightness 11,6" is in different units - not W/m2.
  4. Dec 25, 2014 #3
    How can I convert the absolute brightness of 11.6 into flux?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook