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Although I will only tackle one part of the question, I find the following part of a picture from NRAO/AUI/NSF, S. Dagnello, cited from space.com worth sharing: You see the radial structure of Antares, a red supergiant of spectral type M1.5Iab-Ib, and more specifically The average temperatures of photosphere, chromosphere, and above are given. One can see ...


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Maybe somebody can help me understanding the following quote intuitively: However, by looking at the ratio of two different but related lines - those of iron - we found the ratio itself related to temperature. And it did so in a consistent and predictable way. A particular atom can only be at integer quantum states (Hydrogen is depicted here for simplicity)...


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Stars behave like blackbodys. Not perfect idealized blackbodies, however, the spectrum of a star is close enough to the standard blackbody spectrum. Reason why you can use the Wien's Law to calculate an estimate of its surface temperature: $\lambda_{\rm max} = (0.29 {\rm\, cm\, K}) / T$ Where $\lambda_{\rm max}$ is the frequency of maximum measured emission ...


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For this, its important to understand how temperature increases in a star. Inside a stellar core, there are two forces that are balancing each other out to keep the star in equilibrium. The core pressure that is due to photons generated by chemical reactions inside the core forces the stellar atmosphere outwards (also called radiation pressure) while the ...


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No mass blob of stellar mass is transparent at any wavelength of interest. Opacities $\kappa_{\nu}$(inverse transparency) as function of wavelength becomes really high and broad band at pressures above > 0.1 bars, for all wavelengths. This leads to the optical depths $\tau_{\nu}$ being enormous and as transmission is $T=1-\exp(-\tau)$, you won't be able ...


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