Brightest cluster galaxy

Brightest galaxy within a galaxy cluster

A brightest cluster galaxy (BCG) is defined as the brightest galaxy in a cluster of galaxies. BCGs include the most massive galaxies in the universe. They are generally elliptical galaxies which lie close to the geometric and kinematical center of their host galaxy cluster, hence at the bottom of the cluster potential well.

From Wikipedia, under CC BY-SA. More on occurri.