Peculiar galaxy
Magnitude 11.1
RA: 10h 25m 05.5s
DEC: +17° 09′ 37″

N3239_DSS.jpg

I first observed NGC 3239 last year and was fascinated by its irregular shape along with a picturesque clump of more distant galaxies serving as a backdrop. A triangle of medium bright stars added some foreground sparkle to the scene too – all in all, a lovely field of view in my 28 inch scope. But the conditions weren’t great and I want to come back on a darker night to see more, and last month I did.

With some patient observing and darker skies I had a great time teasing out more detail than I saw last year. My first-look impression of this tidally distorted galaxy is that it’s a lumpy mess. The brightest lumps and knots are HII regions and OB associations, and with extended observation the view is gradually embellished by two tidal tails.

The tail easiest to see is Tail B, which projects nearly due north of the main mass of the galaxy directly toward the northern most star of the triangle mentioned above. It doesn’t quite reach the star and appears broad and diffuse and curves westward. Much more difficult to see is the thin line of knots that extends the tail further west.

Even more difficult is Tail A, the faint loop that seeming originates from the brightest knot of 3239 on its southern edge. So far I’ve only seen the brightest part of the loop where it extends west from the bright knot, and think I’d need a nearly perfect night to see the entire loop with my 28 inch scope. I used 408x for my observations, but also 355x and 476x. The SQM was 21.40.

N3239_Arp263_crop.jpg N3239_Arp263_cropinvert.jpg

By the way, the Tail A and Tail B labels are from a 1990 paper by Karl Krienke and Paul Hodge that includes a nice schematic of the 3239’s structure.

None of the fainter galaxies in the field of view are suspected of interacting with 3239 because they are too far away, so it seems 3239 is the result of two galaxies well into the process of merging into one. None are included in my sketch above, which focuses on only 3239.

However, tracking down the smaller and fainter galaxies is fun if you can tear yourself away from 3239. They’re all around 15th magnitude and are a nice collection of galaxies even without 3239 as a main attraction.

"GIVE IT A GO AND LET US KNOW"