Arp 189 (NGC 4651)

  Arp 189 is yet another member of the Narrow Filaments class.  The Atlas note is "radio source near tail apparently not associated".  This is perhaps my favorite Arp.  It's a Seyfert galaxy with a beautiful classic spiral structure in the main body.  The most striking feature is the massive jet terminating in a distinct arc.  This is best seen in the negative image.

I've not been able to find a great deal of research on this galaxy and most that I have found deals with the Seyfert aspect, not the jet.  My own (probably completely wrong) theory is that a highly energetic event in some earlier era ejected a generally spherical gas shell.  The jet has now caught up with the shell and is exciting a circular region where the impact is occurring.  We are seeing the circular region from the side, making it appear to be an arc.

Click on the color image for a full size version and on the negative image for a full size negative. 

Atlas Image

              

  10-inch Newtonian, SBIG ST2000XM, 84:32:28:28 minutes, 21.7' x 28.9'
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