Question

Consider two stars: the 5,800 K G-type star the Sun, and the 33,000 K O- type star Orionis. Assume that the atmospheres of both stars are pure H and have a density of 1o kg/m. (a)[15 pts] For both stars, what is the ratio of neutral H atoms in the ground, first and second excited states (n 1, 2 and 3) (b) [15 pts] For both stars, what fraction of H atoms are ionized? Note that the electron density n, used in the Saha equation is equal to the density of ionized H atoms for a pure H gas. (c) [10 pts] H I Balmer a absorption comes from the n 2 3 transition; H Lyman α absorption comes from the n-1-.2 transition. How does the line ratio (relative strength) of these two lines differ between the Sun and λ Orionis? Does this depend on the ionization state of H? in which source would both of these lines be extremely weak?

Answer 1