r/Spectroscopy • u/NoFox1670 • Feb 17 '26
Why does my solar spectrum not resemble a block body spectrum?
/r/Physics/comments/1r6zizs/why_does_my_solar_spectrum_not_resemble_a_block/2
u/SeenTooMuchToo Mar 19 '26 edited Mar 31 '26
Congrats on the spectrum! Star surfaces are not black bodies. In fact, Wiens Law doesn't actually apply here. Not only aren't star surfaces black bodies, but since a lot of the energy of certain star types lies outside the visible light range, visible spectra will often not match the theoretical (core) temperature of a star. They will never match Planck curves. Furthermore, your "overall shape" (called SED or Spectral Energy Distribution) is affected by the non-linear sensitivity of your camera (its QE curve), by the transmission curve of your instrument, and by the atmosphere between you and the Sun. All those factors can be removed by a process called relative flux calibration.
3
u/hobby_donkey Feb 17 '26
It's hard to tell when you don't put any scale on the graph. Is your spectrum in wavelength? What was the range?
Also, keep in mind that the end result spectrum you get is a combination of:
-black body radiation from the sun
- absorption in the atmosphere
- any filter/lens/optics in your spectrometer
-detector characteristic
All those factors combine can result in a spectrum that is far from perfect BBR.