Irregular galaxy

A irregular galaxy is a Galaxie which does not show any structure regular or discernible and which for this reason is classified with share in the classification of Hubble of the galaxies. The majority of the irregular galaxies are dwarf galaxies.

It thus does not have any characteristic of the spiral galaxies or the elliptic galaxies. The irregularity can result from several Phénomène S, among which the fusion of similar galaxies of sizes, and deformation under the effect of the gravitational influence of a massive neighbor more (case of the Nuages of Magellan).

The irregular galaxies are generally rather rich in gas and interstellar dust and young stars (stars of population I).

The classification of Hubble recognizes two types of irregular galaxies: Irr I and Irr II .

the galaxies Irr I have some structures but not enough to clearly classify them among the other classes.
the galaxies Irr II do not have any structures making it possible to classify them.

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