Can you tell me SIX or more characteristics for an Irregular galaxy?

Answer 1

Irregular Galaxies

Galaxies that don't fit anywhere else are tossed into the "irregular" category. Peculiar shapes abound.
These galaxies often look disturbed, distorted
Unlike lenticulars, irregular galaxies are often places of rampant star formation. A good example is a companion to our Milky Way -- the Large Magellanic Cloud. It is thought that the LMC may be producing new, young globular clusters (a bit of an oxymoron).
Irregular galaxies are those which do not match the standard Hubble scheme of elliptical, spiral and lenticular galaxies.
There's only one irregular galaxy in Messier's catalog: M82, and this one is a distorted disk galaxy. The distortion is due to gravitational interaction with its larger and more massive neighbor M81.

Another, very similar example is at least mentioned in Messier's catalog, though it did not get a number on its own: NGC 5195, the companion of the Whirlpool galaxy M51, which had been discovered by Pierre Méchain. The only further irregular galaxies known to 1782 are the Large and the Small Magellanic Cloud; these are probably miniature disk galaxies in mutual gravitational interaction, and in interaction with our Milky Way.



Irregular Galaxies:
NGC 2976, faint companion of M81 and M82
NGC 3077, companion of M81 and M82
NGC 5128, peculiar and radio galaxy Centaurus A
NGC 5195, companion of M51
NGC 6822: Barnard's Galaxy, an irregular Local Group galaxy
IC 10, an outlying irregular dwarf member of the Local Group.
IC 5152, an irregular dwarf member of the Local Group.
The Large Magellanic Cloud
The Small Magellanic Cloud (also NGC 292)
Wolf-Lundmark-Melotte (WLM), a remote Local Group galaxy

Answer 2

An irregular galaxy is really defined in terms of characteristics it lacks.

1) It lacks a nuclear bulge.
2) It has no spiral arms.
3) It does not consist mainly of older Population II stars.
4) It is not orbited by a system of globular clusters.
5) It does not have a black hole at its center.
6) It does not have significant angular momentum.