First off, I'm not sure if this question should go here or in the homework section. It is an astronomy homework question BUT there are only physics subtopics and did not want to post it in the wrong section. Let me know if it should be moved to there! 1. The problem statement, all variables and given/known data Consider a nebula consisting of an O star surrounded by an H II region surrounded by an H I region. (That is, assumed that the ionized H II region does extend as far as the edge of the nebula.) Let N be the rate at which ionizing photons are emitted by the O star. (e.g. in units s-1). Assume that the nebula is dust free and made entirely of H (i.e. neglect He and the heavier elements). A. In terms of N, what is the rate at which Ly-alpha photons are emitted by the nebula? B. In terms of N, what is the rate at which Balmer photons (including all Balmer transitions and the Balmer continuum) are emitted be the nebula? C. Describe in detail (and with the help of a diagram) the fate of a Paschen continuum photon emitted as the result of the capture of electron by a proton into the n=3 state. What can happen as a result of this capture? D. Imagine viewing the nebula from a distance. From where is the Ly-alpha emission seen-the H II region, the H I region, or both? Why? 2. Relevant equations (1). E = h*w/c (2). F = L/4*pi*r2 3. The attempt at a solution Start with A and B...This answer must use some probability to give a ratio of lyman alpha photons compared to total photons. Is this going to be the recombination coefficient? I'm getting rung up in my own thoughts and am now confused. Any tip would help get me started...don't do the problem, but maybe a hint! Thanks in advance!