RR Lyrae star

Astron. one of a group of pulsating variable stars found in the halo of the Milky Way, with periods between 1.2 and 30 hours; all have approximately the same luminosity and are therefore used for measuring distances. Also called cluster variable.
[ < NL: RR (variable star designation) of LYRA]

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      any of a group of old giant stars of the class called pulsating variables (see variable star) that pulsate with periods of about 0.2–1 day. They belong to the broad Population II class of stars (see Populations I and II) and are found mainly in the thick disk and halo of the Milky Way Galaxy and often in globular clusters. There are several subclasses—designated RRa, RRb, RRc, and RRd—based on the manner in which the light varies with time. The intrinsic luminosities of RR Lyrae stars are relatively well-determined, which makes them useful as distance indicators.

John Donald Fernie
 

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Universalium. 2010.

Look at other dictionaries:

  • RR Lyrae star — Astron. one of a group of pulsating variable stars found in the halo of the Milky Way, with periods between 1.2 and 30 hours; all have approximately the same luminosity and are therefore used for measuring distances. Also called cluster variable …   Useful english dictionary

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