Arp 227

ARP 227 2016 Dec 4

Object:      ARP 227  (NGC 474) Date:       2016 December 4
Peculiarity:    Concentric rings.
Constellation:           Pisces Time & altitude:  20.40 UT       42º
Catalogue data: Seeing (5 high):                               4/5
            R.A:                1h 20m Transparency (5 high):                3/5
            Dec:                +3º 25 Telescope:     0.5m f4.1 Dob.
            Magnitude:    11.5 Eyepiece:      8mm Ethos      x260
            Galaxy size (mins):  7.1 x 6.3 Filters:            Lumicon Deep Sky


NGC 474 is just E of another galaxy, NGC 470 (12.5m 2.8 x 1.7), which is not part of the Arp object. The concentric rings belong to NGC 474. The catalogue size above is across the rings; the central galaxy is much smaller.

NGC 474 is the smaller but more prominent of the pair due to its bright non-stellar core. The round core sits in an oval halo with the major axis aligned N-S. In deep images the overall impression is circular, not oval. I think what I have seen is due to the (unresolved) brightest arcs in some of the inner concentric rings.

NGC 470 shows more detail visually. It is the larger of the pair and the surface brightness is less. There is only a tiny, faint core.  Although diffuse, there are hints of structure which suggest a face-on spiral. In particular there is a contrast effect on the E edge, due to either a dark lane or a bright knot. There is either a foreground star or bright knot in the halo on the W side.