Two stars have the same spectral type. Star X is in luminosity class III, while Star Y is in luminosity class V. Star X must be larger in radius than Star Y.

Question

Quizplus · Accepted Answer

Luminosity class III stars are giants, meaning they are larger in radius than luminosity class V stars, which are main sequence stars. Therefore, Star X must be larger in radius than Star Y since they have the same spectral type but different luminosity classes.

Two Stars Have the Same Spectral Type