The shortest known period of one of these stars in a binary system is 507 days in S Muscae, leading to the theory that most observed examples are on their second or high crossing of the instability strip.
Cecilia and Sergei Gaposchkin found that a more symmetric subset of these stars found in the Magellanic Clouds are systematically brighter than predicted, and the Baade-Wesselink Method can be used to find their size. The shortest known period of one of these stars in a binary system is 507 days in S Muscae, leading to the theory that most observed examples are on their second or high crossing of the instability strip. Metal-poor examples of these stars are called W. Virginis. A shark-fin curve represents their most distinction feature, which is caused He-plus ionizing to He-two-plus, leading to a pressure gradient and subsequent expansion. For 10 points, name this class of variable star with period longer than RR Lyrae that is often used as standard candles.
Cecilia and Sergei Gaposchkin found that a more symmetric subset of these stars found in the Magellanic Clouds are systematically brighter than predicted, and the Baade-Wesselink Method can be used to find their size.
{Cepheid} Variables