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NW Pegasus Superchain

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#1 IVM

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Posted 01 December 2012 - 10:41 AM

Some further notes from my journal about the observations in Pegasus that I made earlier this year. I called this apparent string of galaxy groups and some actual clusters in NW Peg a "superchain"; whether the string is physically real or not, this idle stargazer felt that some term like this was called for to reflect the grandeur of this stretch of our sky.

August 23, 2012. Cherry Springs, 16”. Instead of continuing Herschel 2500 from NGC 7331, I decided to pursue the marvelous string of galaxy groups that stretches diagonally across chart 46 of Uranometria and involves the NGC 7331 group observed last night.

The chain begins in the NW, across the border in Lacerta, with the pair NGC 7227-8. As observed at 225x with the 8 mm Ethos, the pair is nicely framed. NGC 7227 has a fairly bright (non-Uranometria) star on its S edge, which prevents true detection of its elongation. NGC 7228 is fairly large, elliptical in appearance, and elongated roughly NS. [Both were discovered by Stephan with the 31.5” Foucault reflector in 1872.]

UGC 11950 to its E cannot be located with certainty; the field is near the Lacerta Milky Way and is rich with threshold stars. IC 5180 to the N is fairly bright and sizable but does not exhibit elongation.

To locate the next small group in the chain running SE, I return to 1 Lac. The pair of large NGC 7242 and small 7240 is just S of this star. It is nicely framed by the Ethos. The galaxies are essentially at right angles. The small round MCG+6-49-1 just fits in the field of view to the NE.

[NGC 7242 was discovered by Auguste Voigt in 1865. The discovery aperture is given as 31” in HCNGC. This, however, is the same Foucault silvered-glass refactor in Marseille that was later used by Stephan, whose aperture HCNGC gives as 31.2”. It is commonly referred to as the 80-cm Foucault; Steinicke is more precise and gives the aperture as 78.7 or 78.8 cm. NGC 7240 is a Stephan discovery from 1873. The MCG in the above group is mag. 14.47 according to NED.]

The next group to the SE is the last one before the NGC 7331 group. Its W chain begins with UGC 11995. It is elongated NW-SE and has a star on its SE end. NGC 7264 is large and runs parallel to a pair of stars, which make it difficult to find at first. Once located, though, it is fairly bright an strongly elongated. It points at the much smaller NGC 7263. [The UGC is mag. 14.91. The NGCs were discovered by Marth in 1863 with Lassell’s 48”.]

The SE end of this subchain within the group is anchored by NGC 7265, which seems to be subtly elongated NS and have a stellar nucleus. Its companion UGC 12007 cannot be seen. It is probably obscured by stars in its location. The NGC is the brightest in the subchain. [The UGC is m15.3 according to NED. The NGC was discovered by Stephan in 1876.]

The E subchain in this group is a marvelous NS line of NGC 7273, 7274, and 7276. It is nicely framed by the Ethos and is incredibly compelling. [All three were discovered by Stephan in 1876.]

The group that terminates the chart 46 chain SE of the NGC 7331 group is the largest. It involves a scattered halo of galaxies; I targeted the tight core. It fans from NGC 7401 on its W side. The NGC is elongated NS. [Lord Rosse, 1856.] To its E is a nicely framed pair UGC 12235, 12238. Both galaxies are elongated EW. [Magnitude 14.83 and 14.51.]

Farther E [within the core of the NGC 7401 group] is a chain of 5 MCG and 1 UGC galaxies. The UGC 12242 is comparatively prominent [m14.26] and elongated NW-SE. On its NW end is the small, round MCG+5-54-8. [At mag. 16.12 according to NED, it is among the faintest galaxies I can see with my 16”.] Next in this subchain running S is MCG+5-54-14. It is not seen [m15.5]. MCG+5-54-13 is faint but is glimpsed consistently as a soft glow that appears to be elongated subtly EW [m15.81]. On the S end of the subchain MCG+4-54-17 is a comparatively prominent and concentrated glow [m15.3]. MCG+5-54-12 [m15.5] to its NW is not seen.

[...] September 10, 2012. Cherry Springs. 16”. Clear, humidity 70-80%, around 0 C, transparency solid average by CSC. [...]

[Uranometria] Chart 63, Pegasus

Abell 2666. The dominant galaxy in this 338 Mly-distant cluster is NGC 7768. It is both larger and brighter than the rest and has a high surface brightness. It is elongated EW. To its N in the core [of the cluster] are two MCG galaxies [in Uranometria]. Of these, the proximal and large MCG+4-56-19 is invisible. (There is a haze in the area but identification cannot be positive.) The distal MCG+4-56-14 is the second galaxy to be seen in this cluster. Next NGC 7767 can be located on the other side of -68. It has a * on W edge. Finally the small close companion of the central galaxy, NGC 7765 can be found. It is fairly conspicuous once located. The other close companion, NGC 7766 cannot be seen with certainty presumably because of the superimposed star, even though this star is comparatively faint. [-8 was found by John Herschel in 1828, -5 by Lord Rosse in 1855, and -6 and -7 by Ralph Copeland using the Rosse 72” in 1872.]

The last group in this NW-SE chain of groups has NGC 85 in its center. NGC 80, 83, 90, and 93 are prominent, NGC 81 and 94 comparatively difficult. Most galaxies exhibit elongation. All 13 [Uranometria] galaxies are identified: NGC 79, 80, 81, 83, 85, 86, 90, 93, 94, 96, IC 1542, 1546, MCG+4-2-10. [NGC 79, 86, 94, and 96 are due to Bigourdan (1884, 12” refractor); 80 and 83, to John Herschel, 1828; 81, 85, Copeland, 1873, 72”; 90, 93, Lord Rosse, 1854, 72”.]

#2 helpwanted

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Posted 01 December 2012 - 11:41 AM

Excellent article! Thank you for sharing.






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