Editing RR Lyrae variable (section)

{{short description|Type of variable star}}
{{about|the variable star class|the prototype star of the class|RR Lyrae}}

[[File:HR-diag-instability-strip.svg|thumb|right|upright=1.4|The RR Lyrae variable stars fall in a particular area on a [[Hertzsprung–Russell diagram]] of color versus brightness.]]

'''RR Lyrae variables''' are periodic [[variable star]]s, commonly found in [[globular clusters]]. They are used as [[standard candle]]s 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 classification|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 cluster]]s and the chemistry (and quantum mechanics) of older stars.