RR Lyrae

Definition

RR Lyrae stars are a type of pulsating variable star commonly used as standard candles to measure cosmic distances. They have relatively uniform luminosities and short periods, typically less than a day.

5 Must Know Facts For Your Next Test

1. RR Lyrae stars are found primarily in globular clusters and the halo of the Milky Way.
2. Their brightness varies with periods ranging from about 0.2 to 1.0 days.
3. They are older, low-mass stars that have evolved off the main sequence.
4. Their absolute magnitude is roughly +0.75, making them useful for distance measurement.
5. RR Lyrae variables helped astronomers determine the size and structure of the Milky Way galaxy.

Review Questions

Related terms

Cepheid Variable:

A type of pulsating star with a longer period than RR Lyrae stars, also used for measuring cosmic distances.

Globular Cluster: A spherical collection of stars orbiting the galactic core, often containing many RR Lyrae stars.

Standard Candle:

An astronomical object with known luminosity, used to measure distances in space.