RR Lyrae stars

RR Lyrae stars are a type of variable star that pulsates regularly, causing their brightness to expand and contract over time. These stars are typically older, small, and relatively low in mass, often found in globular clusters. Their brightness varies on predictable schedules, usually within less than a day. Because their intrinsic brightness is well understood, astronomers use RR Lyrae stars as "standard candles" to measure distances within our galaxy and to nearby galaxies, helping map the universe's structure. Their rhythmic pulsations provide valuable insights into stellar evolution and the characteristics of ancient stellar populations.