![]() ![]() The hotter layers above the solar photosphere do have an emission spectrum. The geometry may be different to that shown in the diagram but the result is the same. They are not truly lost though but are merely thermalized again and re-emitted as continuum photons. The 'missing bits' of energy are thus due to the photons reflected back by the chromosphere into the photosphere where they are absorbed (the photosphere can be considered a black body and a black body absorbs all incoming radiations). We are of course unable to see the pure continuous spectrum (bottom left) in case of the sun, as the scattering 'cloud' is a layer all around its surface, but we can see the 'bright line spectrum' emitted by the chromosphere during a total solar eclipse for instance as then the direct sunlight is blocked out. This is schematically illustrated by the following diagram at the atomic resonance frequencies of a given element). It is only that the atmosphere above the photosphere (the chromosphere) scatters light out of the line of sight at those frequencies where the scattering cross section is very high (i.e. The photosphere of the sun does produce an emission spectrum (a Planck spectrum according to its temperature of about 6000K). Is it more correct to say that the radiation is rather being absorbed and re-emitted (i.e., scattered) so many times on its journey through the Sun's atmosphere that it continually loses small "bits" of energy that once it reaches us, the intensity of the re-emitted light is much smaller than the absorbed one (causing a dip in the spectrum)? Or is the gas perhaps so dilute that even that wouldn't work? If not, then again, why do we see an absorption spectrum? However, considering the fact that the chromosphere and corona is so dilute, it would seem that that wouldn't be the case. It seems to me that one of the assumptions being made is that the energy that is absorbed by the various layers are first distributed among the various atoms in the layers, such that the re-emitted light that comes out is the ordinary thermal radiation/blackbody radiation. Now, I already have some doubts about the logic above applying here. (I will note that there was a temperature drop inside of the photosphere itself, but to my understanding the photosphere is opaque to all wavelengths, meaning that it can't pick out the specific wavelengths of the absorption spectrum). So then, why doesn't the opposite happen where instead of dips in the spectrum, we get peaks in it (i.e., an emission spectrum)? However, I checked and found that as you go from the photosphere and into the chromosphere and corona, the temperature rises instead. This is consistent with Kirchhoff's laws and Planck's law for blackbody radiation. I have read that the reason why the Sun produces an absorption spectrum is because the temperature drops as you go away from the center, such that as the various layers of the atmosphere of the sun absorb certain wavelengths, the re-emitted light will have a smaller intensity than the absorbed one, causing a dip in the spectrum (i.e., an absorption spectrum). ![]()
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