Object of the Week October 6, 2024 – Holmberg 802/WBL 695 (NGC 7463/7464/7465, UGC 12313/12321)

[Uwe Glahn]

Galaxy Group in Pegasus

NGC 7463
RA: 23 01 51.8
Dec: +15 58 55
VMag: 12.9
Size: 2.6’ x 0.6’
z: 0.0078

NGC 7464
RA: 23 01 53.8
Dec: +15 58 28
VMag: 13.3
Size: 0.5’ x 0.5’
z: 0.0062

NGC 7465 (Mrk 313, PRC D-42)
RA: 23 02 00.9
Dec: +15 57 55
VMag: 12.3
Size: 2.2’ x 1.8’
z: 0.0066

UGC 12313
RA: 23 01 43.6
Dec: +16 04 04.3
BMag: 14.6
z: 0.0068

UGC 12321
RA: 23 02 18.9
Dec: +16 01 38.7
BMag: 16.7
z: 0.0072

Today we visit an often overlooked group 1° NW of Markab. The two brighter NGC objects were discovered by William Herschel in 1784, NGC 1747 by d'Arrest in 1864.

Main subject are the three NGC galaxies, which are listed and catalogued as Holmberg 802. Both nearby UGC galaxies also belongs to the group and are listed as WBL 695 (Catalog of Nearby Poor Clusters of Galaxies of White et al.). But that's not large enough, because our field also belongs to the NGC 7448 (0.5° west) group (9 members).
Coming back to our field, there is not many scientific stuff out there. The two most interesting paper are from Li and Seaquist [1994AJ....107.1953L] and Merkulova at al. [2012AstL...38..290M]. Li and Seaquist described a membership of all three NGC plus UGC 12313 on the basis of HI observations. Merkulova at al. observed gravitational interaction of NGC 7464 and NGC 7465 but don't find the suspected polar ring in NGC 7465.

The visibility of the group started with very small aperture. I could pick up NGC 7463 and NGC 7465 easily with a 4-inch binocular telescope under good but not perfect conditions. A 8-inch showed all three NGC galaxies, while the faintest NGC 7464 was steadily visible with averted vision under soso conditions. Of course with 27-inch the group burst into bloom. Beside the two ghostly edge-on UGC's, the peculiar morphology of NGC 7463 and NGC 7465 becomes visible. But now it's your turn to observe and hopefully reports some results.

DSS blue, 15'x15'
DSS_15b.jpg

sketch: 8", 229x, NELM 6m0+, Seeing III
NGC7465-Gruppe.jpg
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sketch: 27", 293x, NELM 6m5+, Seeing III
NGC7465-Gruppe_27.jpg
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So, as always, “Give it a go and let us know!”

[Clear Skies]

Nice triplet, Uwe!

Two observations in my log, both from the French Alps.

First one in September 2014 using a 12" SCT @ 179x / 27':

NGC7463 (Holmberg 802A), NGC7464 (Holmberg 802C) and NGC7465 (Holmberg 802B) are all visible:
NGC7463 is the northernmost galaxy: Clearly elongated east to west, brighter in the middle. The brighter core also appears elongated east to west. To the SSE is NGC7464.
NGC7464 is a very faint, small, round patch, difficult to observe without AV.
To the SW is a white mag. 8.5 star (SAO108339), slightly closer than that star is, is NGC7465 to the SE: Brighter than NGC7463 and NGC7464 are, elongated NNW to SSE with a bright nucleus that is visible without AV, otherwise even in brightness.

Rated it 4/10.

Second observation was in October 2021 (session / blog) in my 14" SCT @ 168x / 29':

All three galaxies are visible, a nice view.

A - NGC7463 is the brightest galaxy, a clearly east-west elongated glow, irregular with AV and quite suddenly brighter in a large core that is elongated in the same direction. With AV it is clear that the galaxy gradually faints towards the west and more suddenly towards the east. To the SW is a bright white mag. 6 star (SAO108339).

To the SSE of A - NGC7463 is C - NGC7464: a small, faint, round glow, even in brightness without AV, with AV gradually brighter in the middle, no nucleus visible.

To the ESE of C - NGC7464 is B - NGC7465: Without AV a slightly NNW-SSE elongated glow with an extremely bright nucleus that is very clearly visible. With AV slightly more elongated and quite suddenly slightly brighter in a round core.

This time around I must have liked it better, as I rated it 6/10.

DSF OotW 2024-40 - Holmberg 802 Peg_1.jpeg DSF OotW 2024-40 - Holmberg 802 Peg_2.jpeg DSF OotW 2024-40 - Holmberg 802 Peg_3.jpeg

Here's the guide.

[Steve Gottlieb]

I have several observations of the group with the 13.1-inch to 18-inch scopes, but the only time I saw the interesting structure in NGC 7463 was through Jimi's 48-inch:

At 610x, NGC 7463 is very bright, very elongated at least 4:1 E-W, ~2.0'x0.5'. Unusual structure [nearly edge-on barred spiral] with a fairly bright bar angling across the central section ~SW-NE, ~25"x10". A spiral arm extends west of the bar and a long, low surface brightness tidal arm stretches to the east. NGC 7464, situated 0.7' SE, is just south of the beginning of the eastern arm. The stretched appearance is likely due to an interaction with NGC 7465 2.6' SE. These galaxies, as well as the two described below, are part of the NGC 7448 group.

UGC 12321, located 7' NE, appeared fairly faint, thin edge-on 6:1 sliver WSW-ENE, 35"x6", very small brighter core. A 2' length NW-SE string of 3 mag 11.5-12 stars is close south. The middle star is in this string is an uncatalogued double star with a separation of ~1.8". UGC 12313, located 5.5' NNW, appeared very faint to faint, moderately large, edge-on ~4:1 WNW-ESE, 1.2'x0.3', slightly brighter core, fades out at the tips, overall fairly low surface brightness.