Irregular galaxy

Common card · No. 316011

An Irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure. Other galaxies have an axis of symmetry for their blue-light distribution, which cannot be found in the sporadic organization of irregular galaxies. This absence of structure in an irregular galaxy leads to little density waves in these galaxies. This makes irregular galaxies prime areas to study star formation without the effects of density waves. Collectively they are thought to make up about a quarter of all galaxies. A large chunk of the Local Group is made up of irregular galaxies, most being distant and classified as dwarf irregulars. Irregulars are broken down into two more subcategories along with dwarf. Some irregular galaxies were once spiral or elliptical galaxies but...

Read on Wikipedia · Image NASA, ESA, and The Hubble Heritage Team (STScI/AURA), Public domain