Cepheid variable

Cepheids redirects here. For the fictional species, see "Blind Alley".

A Cepheid variable (/ˈsɛfiːɪd/ or /ˈsiːfiːɪd/) is a type of star that pulsates radially, varying in both temperature and diameter to produce brightness changes with a well-defined stable period and amplitude.

A strong direct relationship between a Cepheid variable's luminosity and pulsation period secures for Cepheids their status as important distance indicators for establishing the galactic and extragalactic distance scales.