Two remaining galaxy types include the irregular, classified as I
and peculiar, classified as P. Both kinds of galaxies are usually
experiencing vigorous star formation.
The Large Magellanic Cloud is the most famous
example of an Irregular Galaxy. It has no bulge, no spiral
arms, just an amorphous grouping of stars in a bar shape. The location
of SN 1987a is near the very large star forming region (pinkish red)
just left of center. This galaxy has a lot of cold gas and dust.
This twisted mess is called a peculiar galaxy.
Peculiar galaxies are frequently caused by collisions of
two galaxies. Collisions strongly effect the evolution of those
galaxies. Can you identify two nuclei? These make up NGC 4038 and
NGC 4039 (the pair is also called Arp244).