cluster variable

English edit

cluster variable (plural cluster variables)

(astronomy) an RR Lyrae variable; a type of variable star commonly (but not exclusively) found in globular clusters
- 1902, Solon Irving Bailey, A Discussion of Variable Stars in the Cluster [omega] Centauri:
  This period, which is exceptionally long for a cluster variable, satisfies the observations fairly well except in a few cases.
- 1913, Solon Irving Bailey, Variable Stars in the Cluster Messier 3, page 160:
  It is a good example of a cluster variable having a large range of variations, a short period, and extremely rapid increase and decrease in light.
- 1950, Leaflet:
  Nearly all of the variable stars found in the other globular clusters had the same characteristics as those found in Omega Centauri. It was five years before a cluster variable was found outside of a globular cluster.
- 1949, Popular Astronomy:
  There are some thirty classical Cepheids, and a few irregular variables, in the globular clusters among the stars brighter than the typical cluster variable.
(cluster analysis) A variable whose values are used to classify data points into clusters; a variable that identifies one of the defining properties of clusters.
- 2011, Sabine Landau, Morven Leese, Daniel Stahl, Cluster Analysis:
  The first model includes the potential cluster variable conditioned on clustering variables already selected, while in the second model the variable is not included.

RR Lyrae — see RR Lyrae