Irregular galaxy

Definition

An irregular galaxy is a type of galaxy that lacks a distinct, regular shape like spiral or elliptical galaxies. They often appear chaotic and have no central bulge or spiral arms.

5 Must Know Facts For Your Next Test

1. Irregular galaxies make up about 25% of all known galaxies.
2. They often contain significant amounts of gas and dust, leading to high rates of star formation.
3. Many irregular galaxies are thought to have been distorted by gravitational interactions with other galaxies.
4. The Large Magellanic Cloud and the Small Magellanic Cloud are two well-known examples of irregular galaxies.
5. Irregular galaxies can be classified into two main types: Irr-I (some structure) and Irr-II (completely chaotic).

Review Questions

• What percentage of known galaxies are classified as irregular?
• Name two well-known examples of irregular galaxies.
• What are the two main types of irregular galaxies?

Related terms

Spiral Galaxy: A galaxy characterized by a flat, rotating disk containing stars, gas, and dust, along with a central bulge composed mainly of older stars.

Elliptical Galaxy:

A type of galaxy having an ellipsoidal shape and a smooth, nearly featureless brightness profile.

Star Formation Rate: The rate at which new stars form in a galaxy, typically higher in irregular galaxies due to abundant gas and dust.