Brightest cluster galaxy

A brightest cluster galaxy is the most luminous galaxy in a galaxy cluster, usually a massive elliptical near the cluster’s dynamical center. Its stars and central black hole often record the cluster’s growth through mergers and gas accretion.

Dynamical friction: A gravitational drag that slows massive objects moving through a background of less massive particles. It causes massive galaxies to lose orbital energy and sink toward a cluster’s center.
Galaxy cluster: A gravitationally bound system containing many galaxies, hot gas, and dark matter. The brightest cluster galaxy is defined by its membership in this larger system.
IC 1101: A giant elliptical galaxy at the center of the Abell 2029 galaxy cluster. It is a prominent example of an exceptionally extended central cluster galaxy.
Fossil group: A galaxy group dominated in optical light by one large galaxy, with a substantial gap to its brightest companions. Its dominant galaxy resembles a cluster central, but the system is a group with a distinctive luminosity gap.
Galaxy merger: An interaction in which two or more galaxies combine through gravity over time. Repeated mergers can build the large stellar body of a central cluster galaxy.
Elliptical galaxy: A galaxy with a smooth, rounded stellar distribution and little organized rotation or ongoing star formation. Most brightest cluster galaxies have the structure and old stellar populations of giant ellipticals.
NGC 1275: The active central galaxy of the Perseus Cluster, also known as Perseus A. Its jets and filaments reveal the interaction between a central galaxy and cluster gas.
Central galaxy: The galaxy located at the center of a dark matter halo or galaxy system. A central galaxy is defined by location, whereas brightest cluster galaxy is defined by luminosity rank.
Cannibalism (astronomy): The growth of a large galaxy by absorbing smaller neighboring galaxies. This process adds stars to the central galaxy as satellites lose their orbits.
Galaxy luminosity: The total energy a galaxy emits as electromagnetic radiation per unit time. The defining rank of a brightest cluster galaxy is based on luminosity within its cluster.

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cD galaxyRelated: Many cD galaxies are the brightest cluster galaxies, though the terms are not identical.