Rood–Sastry type

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A category in a classification scheme for clusters of galaxies, based on the type and distribution of the ten brightest members. cD clusters contain a cD galaxy; B clusters have a binary pair of supergiant galaxies less than ten diameters apart; L clusters have their brightest members approximately in line; F clusters are highly flattened; C clusters have a core–halo structure with four or more of the brightest members near the core and fainter members in a halo; I clusters are irregular with no well-defined centre. The classification was introduced in 1971 by the American astronomer Herbert Jesse Rood (1937–2005) and the Indian astronomer Gummuluru Narasimha Sastry (1937–2008).

Subjects: Astronomy and Astrophysics.

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