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Object of the Week, NGC 7331 & Friends
Object of the Week, NGC 7331, MCG 6-49-45, UGC 12113, PGC 69327 & Friends
R.A.: 22h37m04.3s Dec.: +34°24'59"
Size: 9.1'x 3.4', Magnitude: 9.4
I found it hard to believe this notable galaxy has never been selected as an Object of the Week, so I’m happy to choose it today. NGC 7331, discovered by William Herschel in 1784, is a bright edge-on spiral and has been mentioned several times here on Deep Sky Forum because it is the major signpost to finding the nearby Stephan’s Quintet, about 30 arcminutes to the SSW.
NGC 7331 is about 50 million light-years away in the constellation Pegasus and has several much dimmer companion galaxies in its immediate vicinity, which are all about 10X farther away. There are 4 dim companions on the east side, those being NGC 7335 (mag 14.5), NGC 7336 (mag 15.6), NGC 7337 (mag 15.4) and NGC 7340 (mag 14.5).
SkyTools shows 2 other members on the west side, NGC 7325 (mag 14.9) and NGC 7326 (mag 15.8) but Steve Gottlieb, in his NGC notes, says that these guys are misidentified by the RNGC! Steve tells us that the actual NGC 7325 and NGC 7326 objects are double stars! Megastar shows NGC 7325 as being a double star in Steve’s location but it says that NGC 7326 does not even exist! Not all sources are on the same page about all of this! I’ll go with Steve here...
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Here are both the Sky Tools and Megastar charts…
http://tinyurl.com/2jbph745
http://tinyurl.com/5n7xxcke
… and the differences between them are obvious, regarding the locations of NGCs 7325 & 7326. I wonder if any charting program shows them correctly because these are the only 2 that I have.
This group of galaxies is colloquially known as “The Deer Lick Group”, this name originated by Tomm Lorenzin and his observing friends, who had observed it from an observing site known as the Deer Lick Gap Overlook, in North Carolina, and gave it that moniker (RIP Tomm). The dim companion galaxies are known as “The Fleas”. Here is a terrific APOD of The Deer Lick Group (north is towards the upper right-hand corner)…
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In the eyepiece of my 25” the view is very appealing. NGC 7331 is about 10° from being exactly north-south with a PA of 171 and is intermediate between being face-on and edge-on, which results in the galaxy being about 3 times longer than it is wide. Due to the dust lane along the western edge, this bright galaxy has a sharp edge, resulting in a dramatic light drop-off. I do not see any kind of bar, and the nucleus is drawn out and well-defined with a much brighter center. Only on the best of nights can I tease out any weak details regarding the spiral arms, and the best structure was seen at each end of the galaxy.
Regarding the companion fleas, they are a great test of seeing and transparency. I’ve routinely seen all 4 east of NGC 7331 but with a full magnitude difference among them, sometimes it takes a lot of patience to catch them all when under less-than-perfect skies. 50 years ago, as viewed using my brand-new C-8, I could barely glimpse 2 of the fleas from my regular observing spot in the Anza-Borrego desert in southern California, but I was very happy to do that! :D
As always, give it a go and let us know.
