In the Beta Canis Majoris class of these stars, the opacity of iron at depths where the temperature exceeds 200,000 K causes a Z-bump to form. Sergey Blazhko names an unexplained long-period modulation within a class of these stars which are commonly found in globular clusters. Compression of the atmosphere of these stars increases its (15[1])opacity, which creates a (*) buildup of pressure in response, according to the kappa mechanism describing (10[1])these stars. One can determine the absolute (-5[1])luminosity of a class of these stars from a relation discovered by Henrietta Swan Leavitt. The instability strip of Hertzsprung-Russell diagrams contains the RR Lyrae and Cepheid (-5[1])classes of these stars. For 10 (10[1])points, name this class of stars whose luminosity oscillates at a regular period. (10[1]0[1])■END■