A class of pulsating variable stars with periods less than one day and relatively uniform absolute magnitudes around +0.75, making them excellent standard candles for measuring distances to globular clusters and the galactic halo. They are evolved, low-mass stars that have exhausted their core hydrogen.
Named after the prototype star RR Lyrae in the constellation Lyra, discovered in 1899. The designation 'RR' follows the variable star naming convention established by Friedrich Argelander, where stars are named with letters indicating their order of discovery in each constellation.
RR Lyrae stars are like the universe's cheap lightbulbs - they all shine with nearly the same brightness! This makes them perfect for mapping the structure of our galaxy's halo and globular clusters, revealing that our Milky Way is much larger than early astronomers imagined.
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