RR Lyrae Variable - Discovery and Recognition

Discovery and Recognition

In surveys of globular clusters, these "cluster-type" variables were being rapidly identified in the mid 1890s, especially by E. C. Pickering.

Probably the first star of definitely RR Lyrae type found outside a cluster was Mu Leporis, discovered by J. Kapteyn in 1890.

The prototype star RR Lyrae was discovered prior to 1899 by Williamina Fleming, and reported by Pickering in 1900 as "indistinguishable from cluster-type variables".

From 1915 to the 1930s, the RR Lyraes became increasingly accepted as a class of star distinct from the Cepheids, due to their shorter periods, differing locations within the galaxy, and chemical differences from classical Cepheids, being mostly metal-poor, Population II stars.

RR Lyraes have proven difficult to observe in external galaxies because of their intrinsic faintness. (In fact, Walter Baade's failure to find them in the Andromeda galaxy led him to suspect that the galaxy was much farther away than predicted, to reconsider the calibration of Cepheid variables, and to propose the concept of stellar populations.) Using the Canada-France-Hawaii Telescope in the 1980s, Pritchet & van den Bergh found Lyraes in Andromeda's galactic halo and, more recently, in its globular clusters.