"An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. The shape of an irregular galaxy is uncommon \u2013 they 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.Collectively they are thought to make up about a quarter of all galaxies."@en . . .