cD galaxy

astronomy

Also known as: supergiant elliptical

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 24, 2026

Quick Summary

A cD galaxy is a type of galaxy characterized by its abnormally large and distended shape. These galaxies are consistently found in the central regions of galaxy clusters and are theorized to be the result of multiple galaxies merging over time. This process, sometimes referred to as galactic cannibalism, involves a massive central galaxy absorbing smaller cluster members, with the outer extended disks and multiple nuclei of cD galaxies representing remnants of these past mergers. Astronomers sometimes classify them as supergiant ellipticals, noting they are among the most luminous and brightest galaxies.123

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

5 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

galaxy
Interactions between cluster members
…type of galaxy called a cD galaxy. These objects are somewhat similar in structure to S0 galaxies (see above S0 galaxies), but they are considerably larger, having envelopes that extend out to radii as large as one million light-years. Many of them have multiple nuclei, and most are strong sources…
Read More
…type of galaxy called a cD galaxy. These objects are somewhat similar in structure to S0 galaxies (see above S0 galaxies), but they are considerably larger, having envelopes that extend out to radii as large as one million light-years. Many of them have multiple nuclei, and most are strong sources…
Read More