Irregular galaxies are a type of galaxy, often very small, that have an irregular, nebula-like shape and no spiral arm structure. Many of them, like nebulae, are rich in stars, gas, and dust, while others are older spiral or elliptical galaxies that were perturbed by gravity into unusual shapes. There are two main types of irregular galaxies:
Irr I galaxies appear to have some structure, like a central bar or spiral arms, but are difficult to classify.
Irr II galaxies do not have any consistent structure.
Well-known irregular galaxies in our universe include the Small Magellanic Cloud, Leo A, and IC 10.
| E · S0 · SA · SB · SM · Irr |
dSph · dE · dIrr