Irregular galaxy

An irregular galaxy is a galaxy that does not have a distinct regular shape, like a spiral or an elliptical galaxy.
Irregular galaxies do not fall into any of the regular types of the Hubble sequence. They do not have a bulge in the centre, nor any trace of spiral structure. They are quite common: they may make up a quarter of all galaxies. Most were once spiral or elliptical galaxies but were deformed by gravitational pull. Irregular galaxies also contain abundant amounts of gas and dust.
There are three sorts of irregular galaxies:
The Magellanic Cloud galaxies were once classified as irregular galaxies, but have since been found to contain barred spiral structures.