I was wondering if there's a way to calculate a star's luminosity from apparent magnitude data.

  • 2
    $\begingroup$ You see a distant light. You know it's a light bulb. Can you tell how many watts it has? You know what a 100W lamp looks from 1m distance What do you need to know to be able to determine the power or absolute brightness (=luminosity) of the distant lamp? $\endgroup$ Sep 3 at 21:41

1 Answer 1


You'd need to know the distance to the star first (which you can get using the distance ladder). From there, you can infer the luminosity distance, and then use the flux you measure to calculate the luminosity using the flux-distance relationship.

  • $\begingroup$ This an incomplete answer, since in general, a broadband magnitude does not give you the bolometric flux. $\endgroup$
    – ProfRob
    Sep 12 at 14:21
  • $\begingroup$ @ProfRob you almost surely know more about this corner of astronomy than me, so you should write an answer =) $\endgroup$
    – Allure
    Sep 12 at 14:52

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