On the basis of the graph of absorption line strengths (in Figure 17-12), what is the spectral type of a star with the following spectral pattern: very strong Ca II lines; weaker Fe I lines; equal strength but weaker Fe II and Ca I lines; and no He I, He II, or TiO lines?

Question

Quizplus · Accepted Answer

The very strong Ca II lines suggest a later spectral type, as A and earlier spectral types have weaker Ca II lines. The weaker Fe I lines and equal strength but weaker Fe II and Ca I lines suggest a slightly lower metallicity, characteristic of spectral types later than F. The absence of He I, He II, or TiO lines rules out the M spectral type. Therefore, the best choice is K.

On the Basis of the Graph of Absorption Line Strengths