7

The sun's density is 1 gm/cc at approximately 50% of the way down towards the core. if radius of Sun is R then at R/2 the density will be that of water. @astrosnapper's comment links to this answer in Physics SE. A reverse image search of that unsourced graphic leads to Thesis: Multi-spacecraft analysisof the solar coronal plasma NASA: The Solar Interior ...


7

Well let me take a stab at it. The line in question is said to be a probe of an Fe XI line, that is iron atoms with 10 electrons removed. You do not get such ions in the solar photosphere, it is far too cool; the radiation from the photosphere is probably a pseudo-continuum at that wavelength. However, much hotter material in the chromosphere and corona ...


5

Easily ionised ones like sodium and potassium. Not much from lithium because that is rare. You don't need many free electrons. The fraction of H$^{-}$/H is very small, something like $10^{-7}$ in the solar photosphere. And indeed the number densities of sodium and potassium to hydrogen are of that order.


4

Interesting questions! I hope I can shed some sunlight on them. As stated in the abstract that you quote, understanding and modeling of sunspots is an open question, especially the question how the stability of sunspots is sustained. There are many models, as your citations indicate. First, some terminological clarification: the "Wilson effect" ...


4

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 ...


4

The Sun is pretty much a blackbody for every purpouse except when looking at it with a rather precise spectrometer. Then again, it is not a constant temperature blackbody. The brightness of these images directly translates to some temperature in the corresponding region of the photosphere. The most bright of them are somewhere 6000K, the darkest pixels are, ...


2

I usually don't answer my own questions, but sometimes when the question itself is called into question I make an exception. The density of the photosphere at $\tau_{5000}=1$ is predicted to be $3 \times 10^{-7} \text{g/cm}^3$ in the Holweger-Müller Model Atmosphere7. As pointed out in comments there is a spread in values here. The 1E-06 g/cm^3 density value ...


2

There is no simple answer to these questions - although I could be brief and say (i) No it doesn't and (ii) no they won't. If you make a simple two component atmosphere then the observed spectrum will be the flux-weighted combination of two spectra. $$ S_{\rm obs} = \frac{A_1 T_1^4 S_1 + A_2 T_2^4 S_2}{A_1 T_1^4 + A_2 T_2^4}\ , $$ where $A_1, T_1, S_1$ are ...


1

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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