(Solved): Suppose the spectra of two stars are found to differ, in that Star 1 has strong hydrogen absorption ...

Suppose the spectra of two stars are found to differ, in that Star 1 has strong hydrogen absorption lines, while Star 2 shows no trace of hydrogen absorption. Using concept 15 , the most valid conclusion that you can draw is that: Star 2 probably has no hydrogen in its outer layers. Star 2 is either hotter or cooler than Star 1, but you cannot say which without further information. Star 2 is definitely cooler than Star 1. Star 2 is more distant than Star 1. Star 2 is definitely hotter than Star 1.