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Observation by Alan Snook: Arp 227

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Alan Snook


Alan Snook


2016 Dec 04 - 20:40


2016 Dec 05 - 15:03


Arp 227

  • 0.5m f4.1 Dobsonian
  • 8mm Ethos eyepiece x260
  • Lumicon deep sky filter


Target name

Arp 227 (NGC 474)


Arp 227

About this image

Arp 227 (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. Arp listed this galaxy as an example of concentric rings. The rings belong to NGC 474.

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 the oval halo 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.

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