An Etymological Dictionary of Astronomy and Astrophysics
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Grouping of a number of similar astronomical objects.

Noun from verb → cluster.

An empirical power-law representing the number of stellar clusters as a function of the number of stars per cluster within an interval. It is expressed as: N(N_*) dN_*∝ N_*^-α dN_*, where N(N_*) is the number of clusters containing N_* stars and dN_* is the interval in star number. It is believed that this relationship applies to a variety of systems, including stellar clusters, globular clusters, H II regions (Oey et al. 2004, AJ 127, 1632).

→ clustering; → law.

A model in which a system of self-gravitating particles will gradually aggregate into larger and larger gravitationally bound groups and clusters.

→ hierarchical; → clustering.

Grouping of galaxies in supercluster structure.

→ super-; → clustering