Since an emission spectra represents electrons moving back down to different energy levels and releasing a photon with the energy difference, wouldn't the emission spectra of a star be temperature dependant? Wouldn't the hotter stars have more electrons in higher energy states and so have larger energy releases when they fall back? So my question is do we see that hotter stars have a more pronounced emission spectra in the high frequency range of light, if not, why?


This is not how stars emit light. Stellar emission is thermal radiation for the most part. So while it is true that stars with higher temperatures emit spectra that are shifted to the shorter wavelengths of light, it has nothing to do with excitation and recombination processes in atoms.

There are often certain lines missing in stellar spectra, which is due to the inverse effect you are describing. Atoms on the outermost layers and surrounding a star can absorb some of the thermal radiation to excite electrons in their shells. These lines can be used to determine which elements are present in the vicinity of a star.

  • $\begingroup$ Would it be the case for the emission of light from a hot gas? $\endgroup$ – Vishal Jain Apr 11 at 10:05
  • $\begingroup$ Whenever the term "hot" is relevant in the emission, that's a pretty big hint towards thermal emission. Electronic excitation and relaxation of atoms is ususally a "cold" process, since whenever things are hot, they tend to ionize and form a plasma. Of course "hot" and "cold" are relative, but I think you get the idea. $\endgroup$ – noah Apr 11 at 10:08
  • $\begingroup$ Ah I was asking because in my course we were told atomic spectra depends also on the density of the source, hot and dense (i.e stellar) results in the thermal radiation or continuous spectrum as you mention, hot and not very dense objects (hot gas) have radiation which consists of only particular colours or frequencies. It was introduced as the first two of Kirchhoff's radiation laws. In that sense I'm not sure I understand why the emission of a hot gas is mainly thermal or continuous as it seems to conflict with what I've been taught. $\endgroup$ – Vishal Jain Apr 11 at 10:48
  • $\begingroup$ From wikipedia about star temperature: "Main-sequence stars vary in surface temperature from approximately 2,000 to 50,000 K, whereas more-evolved stars can have temperatures above 100,000 K. " So I think we do see that hot stars have higher frequency light, but thermal radiation in wiki is only in the range of about 3000 to 6000K. Thermal radiation is due more to smaller bands gap transistions between the higher orbitals, stars also have hydrogen which involves a lot of core electron activity which technically is not thermal. $\endgroup$ – PhysicsDave Apr 11 at 13:30

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