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Homework Help: Calculating luminosity given accretion power

  1. Nov 28, 2011 #1
    1. The problem statement, all variables and given/known data

    I have a question regarding calculating luminosity given accretion power. I have accretion power given to me as Δm/Δt= 1.5 solar masses/yr, in order to solve for luminosity are we supposed to convert the accretion power into solar masses/seconds or is it just some kind of variable where it doesn't matter. [I have to find the luminosity in Joules/sec]

    2. Relevant equations

    Luminosity= η x (Δm/Δt) x c^2

    3. The attempt at a solution

    My answer would be that I do have to convert because one joule= kg x m^2/ s^2 and if I have to find the Joules/sec I cannot leave the years unconverted.

    (sorry if it was a dumb question, I think I answered it myself just working through explaining it to you guys)
  2. jcsd
  3. Nov 28, 2011 #2
    Yes, to get an answer in SI units you have to convert the accretion rate into kg/s through the conversions between solar masses to kilograms, and years to seconds. Then, you can use c in m/s and the efficiency will be a dimensionless number, so you can just multiply through and your answer will be in J/s, as you observed.
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