# Homework Help: Hollow spherical shell of gas around a star

1. Oct 14, 2009

### KaiserBrandon

1. The problem statement, all variables and given/known data
f the Sun's atmosphere increased in temperature with radius at and above
the photosphere, how would our observation of the solar spectrum be different?
b) Consider a spherical hollow shell of gas around a star. If you observe this shell to produce
a bright ring around the star, what can you say about the optical thickness of the shell?
c) For the ring in part b, what can you say about its spectrum?

2. Relevant equations
none

3. The attempt at a solution
So for a, I figured that if the temperature is higher, it would produce broader and more intense spectral lines. For b, I'm not sure about whether it's optically thick or thin. If you can still see the star and a ring around it, wouldn't it be optically thin since the photons can pass through the gas...but why does it create a ring around the star? if you can only see a bright ring, would it not be optically thick and the ring is due to the gas absorbing photons and electrons gaining orbitals and coming down and releasing photons...but then why wouldn't you just see one big bright cloud? For part c, there would be absorption lines in the stars spectrum due to the absorption of certain wavelengths of light that is being emitted from the star as it passes through the gas...or am I wrong?

Last edited: Oct 15, 2009