Cephei was the first to be identified (by Goodricke in 1784). Population II Cepheids are sometimes known as W Virginis
stars, after their prototype, W Vir, and a W Vir star is typically a factor of 3 fainter than a classical Cepheid of the same
period.
Cepheids come in two flavours: type I and type II, corresponding to population I and II stars. Population II stars are an
earlier metal-poor generation of stars, which formed after the hypothetical, truly primordial Population III stars, but before
later-generation Population I stars like the Sun which contain significant extra amounts of elements other than hydrogen and
helium due to enrichment of the ISM by supernovae in the meantime. The name “Cepheid” derives from the fact that the star
Cephei was the first to be identified (by Goodricke in 1784). Population II Cepheids are sometimes known as W Virginis
stars, after their prototype, W Vir, and a W Vir star is typically a factor of 3 fainter than a classical Cepheid of the same
period.
Cephei was the first to be identified (by Goodricke in 1784). Population II Cepheids are sometimes known as W Virginis
stars, after their prototype, W Vir, and a W Vir star is typically a factor of 3 fainter than a classical Cepheid of the same
period.