Last modified on September 21, 2017, at 18:19

Irregular galaxy

image of irregular galaxy

An irregular galaxy is a type of galaxy that has no obvious symmetry and structure.[1] Irregular galaxies account for around 3% of galaxies in the night sky, though some estimate it is closer to 20%.[2][3] An example of an irregular galaxy is the Large Magellanic Cloud.

Classification

Irregular galaxies are split into two groups, "Irr I" and "Irr II".[1] 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.

Meanwhile, Irr II galaxies tend to be red and also contain large amounts of dust.[1][4] This dust makes it very difficult to identify individual stars in a type Irr II galaxy.

References

  1. 1.0 1.1 1.2 Galaxies from britannica.com
  2. Irregular galaxies from cas.sdss.org, Sloan Digital Sky Survey estimates abundance of irregular galaxies is around 3%
  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
  4. Galaxy classification from astro.cornell.edu