GALAXIES A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z           HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site irregular galaxy The irregular galaxy NGC 4490. Image courtesy Richard Crisp A galaxy, with a poorly-defined structure, that falls outside the categories of disk galaxy or elliptical galaxy. Two main types are recognized in the Hubble classification scheme. Type Irr I galaxies are less massive (108 to 1010 solar masses) than large ellipticals or spirals and often have a high gas content and show evidence of extensive star formation. Type Irr II galaxies make up a catchall group that may, in some cases, include interacting and merging systems. Small irregular galaxies that appear to be completely non-uniform in shape are known as dwarf irregular galaxies. A nearby example of an irregular galaxy is the Sagittarius Dwarf Irregular (SagDIG). Related category    • GALAXIES Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP