27
votes
Do stars become more metal-rich as they evolve?
If the star is a solar mass or below it will not produce any metals (anything heavier than helium) within 10 billion years of birth. It will be on the main sequence, fusing hydrogen to helium via the ...
- 140k
15
votes
Do stars become more metal-rich as they evolve?
Yes, it will
Metals in astronomy, are simply elements that are heavier than hydrogen and helium. From that perspective, even oxygen and carbon are "metals" in a astronomical sense, although ...
- 2,022
8
votes
Accepted
At what depth below the Sun's surface does the density reach that of water?
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 ...
- 4,456
7
votes
Accepted
What does this "web on the surface of the Sun" image reflect? What does 789 nm show us?
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 ...
- 140k
5
votes
Accepted
What class of elements are providing the many electrons needed to make the H- ion?
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 ...
- 140k
4
votes
Accepted
Wilson effect: How "deep" are sunspots?
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 ...
- 4,439
4
votes
Are any supergiants translucent?
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 ...
- 5,504
4
votes
What does this "web on the surface of the Sun" image reflect? What does 789 nm show us?
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 ...
- 2,776
3
votes
Accepted
What is the density profile within the Sun's photosphere? Which one of these is wrong?
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 \...
- 31.6k
2
votes
Distance between "inside" and "outside" of the sun?
You're asking about the Sun's photosphere, a thin (~250 km thick) layer inside of which the odds of a photon escaping are less than 50% and outside of which the odds are close to 100%. The fuzzy ...
- 33.3k
2
votes
Do neutron stars have something like a gamma-ray photosphere? Are gamma rays from below it limited more by the nuclei or electrons?
Most neutron stars? I would think not. The cooling time for a neutron star is initially seconds due to neutrino emission and thermal conduction is very effective, so the bulk of the neutron star will ...
- 140k
2
votes
What effect does stellar granulation to have on a chemical analysis of a star's spectrum?
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 ...
- 140k
1
vote
Are any supergiants translucent?
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 ...
- 9,584
Only top scored, non community-wiki answers of a minimum length are eligible