IC51 by geckzilla on Flickr.

Via Flickr:
IC51 is kind of a confusing galaxy. It’s got elliptical shells but it’s also got dust and and a relatively large central disk, keeping it from fitting neatly into any category. It’s simply listed as “interacting galaxies” in SIMBAD but it’s progressed so far that it appears as a single galaxy to me.

Red: hst_06276_06_wfpc2_f814w_wf_sci
Green: hst_06276_06_wfpc2_f555w_wf_sci
Blue: hst_06276_06_wfpc2_f675w_wf_sci

Arp 230

Arp 230, or IC 51, is a lenticular galaxy- one with a disk shape and central bulge, but no clearly defined spiral arms. These galaxies are considered intermediates between spiral and elliptical galaxies. Arp 230 is rather small for a lenticular galaxy, and was probably formed by the collision of two galaxies each smaller than the Milky Way.

The collision of the two galaxies is likely responsible for Arp 230’s odd, irregular shape. The galaxy also displays a polar ring, the outer ring of stars and gas orbiting the poles. The theory is that the smaller of the colliding galaxies orbited perpendicular to the larger galaxy’s disk, and was ripped apart during the merger. This may be responsible for the structure of the polar ring.

Image and information from NASA.