An irregular galaxy is a type of galaxy that has no obvious symmetry and structure. Irregular galaxies account for around 3% of galaxies in the night sky, though some estimate it is closer to 20%. An example of an irregular galaxy is the Large Magellanic Cloud.
Irregular galaxies are split into two groups, "Irr I" and "Irr II". Type Irr I is much more common than Irr II and have similarities with spiral galaxies such as containing mostly blue stars and some have a bar. They do not have any arms and have a very small nucleus if any, and so are sometimes considered an extension of the Sc class of spiral galaxies on the Hubble tuning fork diagram.
- Galaxies from britannica.com
- Irregular galaxies from cas.sdss.org, Sloan Digital Sky Survey estimates abundance of irregular galaxies is around 3%
- What is an irregular galaxy from coolcosmos.ipac.caltech.edu, the Infrared Processing and Analysis Center as NASA estimates irregular galaxies make up for 20% of all galaxies
- Galaxy classification from astro.cornell.edu