I'm beyond an amateur, but I've been failing to find this information and it makes me think I'm missing something.

Anyway: I am trying to write a procedurally generated simulation that includes different stars of different types. I want to be able to describe their output in different wavelengths, from radio to gamma rays. It doesn't need to be perfect or precise, I just want to have a vector for about how much of their energy is released as radio waves, infared, etc. I want to be able to make rough estimates of how much radiation of different types planets at different distances would be subject to. It would be great to also have some notion of the frequency and intensity of events like sunspots or flares.

That seemed like an easy enough question, but I've been unable to find the information even for the sun, let alone a "typical" range for a star. (So far I've found one image that graphs sunlight, but only in the IR-UV range and it would be tough to translate to a vector.) I can find a lot of claims that such-and-such sort of star emits a lot of so-and-so radiation, but not hard numbers.

For my purposes specific (narrow) spectral lines aren't important.


  1. Am I thinking about this completely wrong? Is there a reason I can't quantify light in this way?
  2. Does anyone know where I could find this information? Ideally a chart of proportional energy in each range for each star type, but anything I could build that from would be good.
  3. How can I relate "normal" energy output to specific events like flares?
  • $\begingroup$ Why do you want the flux outside of the UV to IR range? If you are interested in energy output then I can tell you that this fraction is $<0.01$ outside of 300-10,000 nm. $\endgroup$
    – ProfRob
    Commented Jul 30, 2021 at 14:29
  • $\begingroup$ Some stars produce significant amounts of x-rays or even gamma rays, right? Even if it's not a relevant fraction of their total output, I want to be able to describe how much radiation in those bands a planet/ship/whatever would be subject to. $\endgroup$ Commented Jul 30, 2021 at 16:15
  • $\begingroup$ @EdwardPeters Not really. If you look at the Figure 1 in that article, that plots X-ray luminosity as a fraction of the overall (bolometric) luminosity. The most energetic stars are around 10^-3 or 0.1% of the energy coming out as X-rays; some are 4 orders of magnitude lower than this $\endgroup$ Commented Aug 2, 2021 at 23:24
  • $\begingroup$ @astrosnapper I mean, .1% of a star's radiation sounds plenty significant to me. If you're just measuring energy output it might not be, but if you're an astronaut/organism/planet/whatever that's shielded from the IR-UV band then X-rays could still be dangerous, right? $\endgroup$ Commented Aug 3, 2021 at 15:43

1 Answer 1


A friend of mine may have answered this for me: he said to basically assume stars act as black body radiators, in which case I can find what I want from Planck's law and some calculus.

  • 1
    $\begingroup$ This works ok for wavelengths between about 400nm-10,000 nm. Outside this range it will be very poor, and a huge underestimate for UV and X-ray radiation, which depend on more than just the type of the star. $\endgroup$
    – ProfRob
    Commented Jul 22, 2021 at 21:21
  • $\begingroup$ @ProfRob do you know a more accurate way to find those values? $\endgroup$ Commented Jul 22, 2021 at 22:15

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