Dwarf elliptical galaxy

A low-luminosity, compact galaxy with an elliptical shape, little cold gas, and generally older stars. Many orbit larger galaxies and have been reshaped by their environments.

Elliptical galaxy: A galaxy with a smooth, ellipsoidal stellar distribution and little organized rotation or cold gas. Dwarf ellipticals are low-luminosity members of the broader elliptical-galaxy family.
Ram-pressure stripping: The removal of a galaxy's interstellar gas by pressure from its motion through surrounding hot gas. It can deprive an infalling dwarf of gas needed for continued star formation.
Fritz Zwicky: A Swiss astronomer who proposed dark matter and made influential studies of galaxies and galaxy clusters. Zwicky introduced the term 'dwarf elliptical' in describing faint galaxies in the Coma Cluster.
NGC 205: A dwarf elliptical galaxy and satellite of Andromeda, also known as Messier 110. Its central young stars and dust show that some dwarf ellipticals retain traces of recent activity.
Dwarf spheroidal galaxy: A very low-luminosity galaxy dominated by stars and dark matter, with a diffuse, spheroidal appearance. Its diffuse structure contrasts with the relatively compact form of dwarf ellipticals.
Tidal stripping: The removal of stars or gas from an object by gravitational forces exerted by a nearby massive body. A massive host can strip material from a dwarf elliptical and alter its structure.
Walter Baade: A German-American astronomer who distinguished stellar populations and resolved stars in nearby galaxies. Baade helped establish the distinction between compact dwarf ellipticals and diffuse dwarf spheroidals.
NGC 185: A dwarf elliptical galaxy in the Local Group with dust and a small amount of gas. It illustrates that the class is not uniformly devoid of interstellar material.
Galaxy morphology: The classification of galaxies by visible structure, including shape, spiral arms, and central components. Morphology distinguishes dwarf ellipticals from disks and diffuse dwarf spheroidals.
Galaxy harassment: Repeated, rapid gravitational encounters that heat and reshape galaxies in dense environments. Encounters in clusters can transform smaller galaxies without a single direct merger.

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Faber–Jackson relationBroader topic: Dwarf ellipticals can depart from the relation defined by brighter elliptical galaxies.