Back RR Lyrae-ster Afrikaans متغير RR القيثارة Arabic Variable RR Lyrae Catalan Hvězdy typu RR Lyrae Czech RR Lyrae (stjerne) Danish RR-Lyrae-Stern German Μεταβλητοί αστέρες RR Λύρας Greek Estrella variable RR Lyrae Spanish RR Lyrae izar aldakor Basque متغیر آرآر شلیاقی Persian
RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype and brightest example, RR Lyrae.
They are pulsating horizontal branch stars of spectral class A or F, with a mass of around half the Sun's. They are thought to have shed mass during the red-giant branch phase, and were once stars at around 0.8 solar masses.
In contemporary astronomy, a period-luminosity relation makes them good standard candles for relatively nearby targets, especially within the Milky Way and Local Group. They are also frequent subjects in the studies of globular clusters and the chemistry (and quantum mechanics) of older stars.