Object of the Week, NGC 7331 & Friends

[Paul Alsing]

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...

n7325.jpg

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)…

NGC7331Web4_goldman.jpg

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!

As always, give it a go and let us know.

[obrazell]

Actually it was covered in 2017 by Rolando

[Clear Skies]

One observation to share since I last posted about this group.

5 October 2018 in the French Ardennes, 14" SCT @168x / 29':

NGC7331 (Holmberg 795A) is elongated NNW-SSE, suddenly brighter in a core that is elongated in the same direction and that is slightly SSE of the middle. The nucleus is visible without AV.
NGC7337 (Holmberg 795B) is visible SE of NGC7331, an extremely faint glow, slightly elongated north to south. With AV a mag. 13 star is visible on the eastern edge (4UCAC622-127602).
ENE of NGC7331 is NGC7335 (Holmberg 795C), brighter than NGC7337 is, without AV slightly elongated NNW to SSE, with AV more elongated and quite suddenly brighter in the middle; without AV only the brighter core is visible.
The star 4UCAC623-129719 (NGC7338, Holmberg 795D) is visible to the east of NGC7331.
East of the star NGC7338 (Holmberg 795D) is the galaxy NGC7340 (Holmberg 795E), a north-south elongated glow, even in brightness without AV, with AV clearly brighter in the middle.
Two stars that form NGC7325 (Holmberg 795) are visible, aligned NNW to SSE, the NNW star is the brightest. The galaxy 2MASX J22365123+3423047 NE thereof is not visible.
NE of NGC7331 and SW of two mag. 11.5 stars aligned NNW to SSE the star that is Holmberg 795G is visible with AV.
A star that forms NGC7326 (Holmberg 795H), WNW of NGC7331 is at the limit of visibility without AV.
The star 4UCAC623-129682 (NGC7333, Holmberg 795I) is visible with AV to the NE of NGC7331, very faint. West thereof is a mag. 13 star.
The galaxy NGC7336 (Holmberg 795J) is visible NNE of NGC7335 (Homberg 795C), a faint, round glow, even in brightness, no detail visible. To the SSE is a mag. 13 star.

1/4 FoV to the NW of NGC7331 is an elongated triangle of three mag. 11 and fainter stars pointing SW. The NW star in the base on the NE side is 4UCAC623-129632 (NGC7327), the galaxy PGC69291 is the background cannot be discerned.

NW of the star designated NGC7327 is a mag. 12.5 star with the galaxy MCG+06-49-044 (PGC69281) to its NNW: A NE-SW elongated, faint glow, even in brightness. With AV gradually subtly brighter in the middle.

Holmberg 795-1.jpg Holmberg 795-2.jpg Holmberg 795-3.jpg Holmberg 795-4.jpg Holmberg 795-5.jpg

Click here to download the observing guide.

[Raul Leon]

Hi,here's my observation from 10/11/2007: Ngc 7331(ngc 7337, ngc 7335,ngc 7340), aka as the Deer Lick group; always a stop off point to Stephen's quintet, this group is really nice especially ngc 7331, which resembles a small Andromeda galaxy. I used a 10mm Radian at 198x with my 14.5 StarStructure f/4.3
ngc 7331.jpg

[Paul Alsing]

Actually it was covered in 2017 by Rolando

Well, I was led to believe that using this Google search...

“NGC 7331” site:www.deepskyforum.com

... it would find everything! I guess not...

My apologies...

[wvreeven]

Remember that there is the Google Doc that contains all OOTW.

[Uwe Glahn]

I've recorded a very challenging but clear sighting of the galaxy with a 8x30 binocular.

The 4-inch binocular telescope shows a direct vision galaxy with an 1:2 elongation.

With the 14.5-inch all companions were visible and the somewhat irregularly halo of NGC 7331.

sketch: 14.5", 202x, NELM 6m5+
NGC7331.jpg
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