Interacting Galaxy System KPG 592 (NGC 7769, NGC 7770, NGC 7771)

[deepskytraveler]

Constellation: Pegasus

NGC 7769, UGC 12808, MRK 9005
Type: Galaxy, AGN LINER
Morphology: (R)SA(rs)b
RA: 23h 51.1m
Dec: +20° 09’ 01”
Mag: 12.0v
SB: 12.8
Size: 1.6’x 1.6’

NGC 7770, MCG+03-60-034, UGC 12813
Type: Galaxy
Morphology: S0/a?
RA: 23h 51.4m
Dec: +20° 05? 47?
Mag: 13.8v
SB: 13.3
Size: 0.9’x 0.8’

NGC 7771, MCG+03-60-035, UGC 12815
Type: Galaxy, star-burst
Morphology: SB(s)a
RA: 23h 51.4m
DEC: +20° 06? 43?
Mag: 12.2v
SB: 13.1
Size: 2.3’ x 1.1’

The three galaxies (NGC 7769-7771) comprise this interacting galaxy system known as KPG 592. The KPG identifier (Karachentsev Pairs of Galaxies) is from the 1972 work by Igor Karachentsev “Isolated Pairs of Galaxies in Northern Hemisphere (https://ned.ipac.caltech.edu/level5/Sept02/Keel/Keel2_4.html).” This trio of 12th to 14th magnitude galaxies lie within the Great Square of Pegasus, about 200 million light-years away.

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NGC 7769 and NGC 7771 are both 12th magnitude spirals, about 2' apart. NGC 7769 is the westernmost member of the trio. It is round with a bright, compact center, while NGC 7771 is highly elongated east-west with a star-like nucleus. NGC 7770, located immediately southwest of NGC 7771, looks at first like a 13.5-magnitude star, but at high magnification reveals itself as a dense, fuzzy smudge of light. NGC 7770 is a lenticular galaxy with a double nucleus oriented east-west.

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The galaxy in the proceeding finder chart labeled MAC 2351-2006 has been cataloged as NGC 7771A. NED data indicates its magnitude at 17.1v. Current studies indicate NGC 7771 is undergoing a direct encounter with NGC 7769 and NGC 7771A. There is an enormous counter-tail suggesting that both galaxies have already passed very closely. Radio observations show that entire system is embedded in a common envelope of cold molecular hydrogen. NGC 7771 has a bright center with clumpy knots of emission along the central bar. Two arms extend off the base; the southern arm ends in a knot of bright emission while the north arm ends in a luminous arc. An arc is also seen extending away from the joint between the bar and the southern arm to surround the companion NGC 7770.

Before you go explore I leave you this image of the KGP 592 galaxy system to ponder.

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Image by Kent E. Biggs, Columbus TX

Now it is your turn. Give it a go and let us know.

[Clear Skies]

This Karchentseva pair is in fact part of a Karachentseva triple: KTG 82. This trio was earlier recognised as such by Holmberg, who added it as nr. 820 to his list of Double and Multiple Galaxies.

NGC7771 = Holmberg 820A = KTG 82C = KPG 592B
NGC7770 = Holmberg 820B = KTG 82B
NGC7769 = Holmberg 820C = KTG 82A = KPG 592A

In October 2017 I logged one observation, using my 14" SCT @ 168x / 29':


NGC7770 and NGC7771 are the ESE galaxies, NGC7769 is the WNW galaxy.
NGC7771 (Holmberg 820A) is the large NNE galaxy of the two ESE galaxies, elongated ENE to WSW, brighter in the middle, with AV it is clear that it's an elongated, brighter core. The nucleus is visible and appears to be just SW of the middle.
NGC7770 (Holmberg 820B) is the small SSW galaxy of the two ESE galaxies, small, slightly fainter than NGC7770 and slightly elongated ENE to WSW. Even in brightness without AV, with AV gradually slightly brighter in the middle.
The faint galaxy NGC7771A (PGC214933) to the west is not visible.
NGC7769 (Holmberg 820C) is the WNW galaxy: A slightly north-south elongated, oval glow, brighter in the middle. With AV the nucleus is visible along with a faint, outer halo.

Rated it 6/10.

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Click here (https://clearskies.eu/csog/downloads/dsfootw#21-35) for the observing guide for this week's OOTW.

[Raul Leon]

Hi here's my observation from 10/25/2014 : ngc 7769 galaxy in Pegasus : mag: 11.69, the brightest member is circular halo with bright nucleus, Ngc 7771 is mag: 12.93 and elongated and Ngc 7770 is mag: 14.4 roundish and very faint. I used a 10mm Ethos at 198x with my 14.5 Starstructure Dob f/4.34441

[lamperti]

With a 20" at 318x: NGC 7771: Brightest of the three. The core seems granular and images later showed numerous H-II regions.
NGC 7769: Large and very obvious. In the same field as NGC-7771 and 7770. Bright core.
NGC 7770: Small and round

[wvreeven]

This is not a competition but wiht my 20" I was able to apply a higher magnification:

NGC 7769 is a reasonably large oval smudge. At 545x I get the feeling that I see the start of a spiral arm on the north eastern side.
NGC 7770 is a small, compact slight oval with a stellar nucleus.
NGC 7771 is an elongated, long, oval smudge with a stellar nucleus. On the side of NGC 7770 it ends shaprly but I don't see more galaxy beyond this sharp edge.

[Uwe Glahn]

Found two results of the group itself and the pair 7770/7771.

sketch: 16", 300x, NELM 6m5+
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home (http://www.deepsky-visuell.de/Zeichnungen/NGC7769-Gruppe.htm)


sketch: 27", 586x, NELM 6m5+
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home (http://www.deepsky-visuell.de/Zeichnungen/NGC7770_NGC7771.htm)

[Ivan Maly]

Here are my 2012 notes, and a labeled DSS. 16", club site.



https://4.bp.blogspot.com/-wprX8oZXrJ4/UQ011aRy-kI/AAAAAAAAAWc/pkTLoLDlGDI/s400/NGC+7769,+70,+and+71+blue+DSS.jpg (https://www.blogger.com/blog/post/edit/658677426095808866/5956421596583858847#)


NGC 7769 (II.230) and NGC 7771 (II.231) form a triple system with NGC 7770. The last one is strongly interacting with 7771. It is not attributed to Herschel, which is almost certainly a mistake, because Herschel’s description of 7771 reads, “contains a stellar nebula or a star”, which must refer to the component now called NGC 7770. [Lord Rosse is credited with discovering NGC 7770 in 1850.] MCG+3-60-31 just to the N in the same field is in Uranometria. Two more faint galaxies can be seen between -69 and -71 on DSS.

At 45x, the two major galaxies look a little like the M81-82 pair in a binocular field. 225x brings out NGC 7770.
The Uranometria MCG galaxy to the N can be located with care; it is a soft little glow.

The “anonymous” edge-on W of NGC 7771 can be glimpsed consistently. Whether its EW elongation (at the correct angle) is due to the invisible star just S of its E end cannot be determined, but the brighter star SW of its W end is clearly separated visually. [The edge-on is PGC 214993 and known as NGC 7771A. The invisible galaxy ENE of NGC 7769 is PGC 214992.]

Both large NGCs have faint starlike nuclei. A faint extension just past NGC 7770 can be seen extending WSW from the N side of 7771 like an arm. Comparison with the DSS in Bratton’s book, however, shows that while the end of the “extension” as seen visually is indeed the interaction plume, its connection to the body of the galaxy from the N is illusory. The “root” of the “arm” that I see is the sharp bright bend of the real arm that curves eastward, whereas the plume in reality extends to the W from the arm that runs S of the core. The field, including the two non-NGC galaxies, is nicely framed by the Ethos.