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ring galaxyA very rare type of galaxy that has the form of an elliptical ring either with a massive nucleus, often off-center, or with little or no luminous material visible in its interior. In many cases there is a small satellite galaxy devoid of interstellar gas. The ring configuration is thought to be unstable and it has been suggested that these systems may represent the after-effects of a collision between two galaxies.
ring galaxy[′riŋ ‚gal·ik·sē]
A class of galaxy whose ringlike structure has clumps of ionized hydrogen clouds on its periphery, may have a nucleus of stars, and is usually accompanied by a small galaxy; probably formed when a small galaxy crashes through the disk of a spiral galaxy.