was the first to detect a variation in brightness, in 1913. Beta Canis Majoris and Sigma Scorpii were found to be variable not long afterwards, Vesto Slipher noted in 1904 that Sigma Scorpii's radial velocity was variable, and R.D. Levee and Otto Struve concluded this was due to the star's pulsations in 1952 and 1955 respectively. These variables were often called Beta Canis Majoris variables because Beta Canis Majoris was the most closely studied example in the first half of the 20th century, though its location in the southern sky meant that its lowness in the sky hampered observations. However, Beta Cephei was the first member of the class to be discovered and so they are generally called Beta Cephei variables—despite the similarity of name (and risk of confusion) with Cepheid variables. Cecilia Payne-Gaposchkin and Sergei Gaposchkin catalogued 17 probable members of the class in their 1938 Variable Stars, though classified them with Delta Scuti variables. 16 Lacertae was another star extensively studied before 1952. The number known jumped from 18 to 41 in 1966. Otto Struve studied these stars extensively in the 1950s, however research declined after his death. Christiaan L. Sterken and Mikolaj Jerzykiewicz classed 59 stars as definite and 79 more as suspected Beta Cephei variables in 1993. Stankov listed 93 members of the class in a 2005 catalogue, plus 77 candidates and 61 poor or rejected stars. Six stars, namely Iota Herculis, 53 Piscium, Nu Eridani, Gamma Pegasi, HD 13745 (V354 Persei) and 53 Arietis had been found to exhibit both Beta Cephei and SPB variability. In 2021 β Cru became the first star of any kind to have its pulsation modes identified using polarimetric asteroseismology. List of Beta Cephei variables List of former, excluded or candidate Beta Cephei variables References