EYEPIECES/MAGNIFICATIONS: Parks Gold Series Plössls (30 mm, 20mm, and 7.5 mm), Parks Gold Series 2x Barlow (30x, 45x, 60x, 90x, 120x, 240x)
FILTERS: Parks ALP Filter, Lumicon OIII Filter
This month's trip to the mountains of southern California was spent tracking down a handful of elusive galaxies scattered across a vast swath of central Pegasus. Here the pickings are slim indeed for the user of small- to medium-sized scopes. Three maps are provided to guide those who would join me in this trek across a celestial desert. The first region begins where our last tour left off, in the eastern regions of Vulpecula, northern Delphinus and western Pegasus. The second region carries us into the heart of the Great Square of Pegasus, and the third region sees us through to eastern side of the Winged Horse and onward into southern Andromeda and the northern spur of Pisces. The deep-sky objects here, all galaxies, are small and faint; there is no eye-candy here, only the spectral glow of ancient photons at the weary end of their journey of tens or even hundreds of millions of years.
The charming double star Gamma (γ) Delphini provides an excellent starting point for our journey; one easily located as the nose of the Dolphin. This pair is easily split at low power, though a little additional magnification will improve the view dramatically, displaying a nice color contrast of yellow and turquoise blue. We will sample a few other stellar offerings before we arrive at our first galaxy. Slip 2° north and a little west and you'll find the semiregular variable star U Delphini. This red giant star fluctuates in magnitude from magnitude 7.6 to 8.9 with a period of roughly 110 days. I estimated its magnitude at "around 8" but I've never been much of a variable star observer and was pretty much content to savor the ruddy glow of this star for a few minutes before moving on. If you are interested in tracking the brightness changes in this object check back every week or so over the next few months before it becomes lost in the western twilight. From U Delphini hop 5° northeast to 33 Vulpeculae and then sweep 2.8° due east to reach Σ 2769 (6.9, 7.7; 17.9"; 300°), a fine pair of white stars, easily separated. From here drop 2.5° south to the 8th-magnitude star SAO 106894 and then 2.7° east to reach 1 Pegasi (4.1, 8.2; 36.3"; 311°) an interesting pair of unequal brightness exhibiting colors of deep yellow and bluish-white.
NGC 7177 (H.II.247): From 1 Pegasi, drop 2.2° due south and then slew 9.1° east to reach the challenging little galaxy NGC 7177. You will pass the bright stars 9 and 13 Pegasi on your way there. Just east of 13 Peg, you may notice a trio of 8th-magnitude stars in a short, shallow arc pointing northwest at the northern edge of your field of view. This group may be used as a landmark for a quick detour to Σ 2841 (6.4, 7.9; 22.3"; 110°) located 1.6° due north. Kepple & Sanner describe this pair a yellow and greenish; I found yellow and yellowish-white. The generous separation of the component stars makes this double an easy mark in any telescope. At 30x, NGC 7177 is barely detectable with averted vision as a small nebulous cloud, featureless and shapeless. A magnification of 60x allows us to view the galaxy with direct vision and reveals an oval shape, elongated east to west and containing a slightly brighter middle. At 120x the bright center seems to be elongated roughly north to south with the southern portion being brightest. (I believe this off-center "nucleus" may be due to a faint field star superimposed on the galaxy.) NGC 7177 is a multi-armed spiral with fragmented arms, similar in its outer regions to NGC 488 in Pisces. Its inner regions are quite different, however, with the inner arms originating on the rim of a high-surface brightness ring (Sandage, 1994). Two supernovae have been observed in this galaxy, in 1960 and 1976 (Boffi, 1999). NGC 7177 has a LINER nucleus (NED). This galaxy lies at an estimated distance of 63 million light years (Strong & Sinnott, 2000). Before we leave the vicinity of NGC 7177, sweep 3.3° east and a little south to pay a quick visit to Σ 2877 (6.5, 9.7; 16.0"; 13°), a fine pair, easily split with colors of deep yellow and blue.
NGC 7332 (H.II.233): To reach our next object, drop back 1° west from Σ 2877 and sweep northward just over 2° to a wide pair of 6th- and 8th-magnitude stars, then slew eastward again 6.7° to reach 40 Pegasi. NGC 7332 lies 4.3° almost due north of this star between a pair of 7th magnitude suns. At low magnifications (30x) this galaxy is discernable as a small silvery cloud elongated northwest to southeast. The center seems quite bright with averted vision. At 60x, NGC 7332 is quite obvious as a slender needle of light with a bright center. It is also seen to have a faint companion galaxy, also highly elongated, to the east. This is NGC 7339 (H.II.234); it has a much lower surface brightness than NGC 7332, but the two make a charming pair nonetheless. At 120x, NGC 7332 is also seen to have a bright box-like core with a nearly stellar nucleus at its center, while NGC 7339 appears somewhat asymmetrical with a slightly brighter center offset to the west (or perhaps the eastern side of the halo is simply brighter than the western). A 12th-magnitude star lies off the southern tip of NGC 7332 and a 13th-magnitude star lies between the two galaxies. In spite of their apparent proximity, there is no evidence of interaction between NGC 7332 and NGC 7339. (de Vaucouleurs, 1964). NGC 7332 lies at an estimated distance of 63 million light years (Strong & Sinnott, 2000).
NGC 7741 (H.II.208): From NGC 7332, we'll sweep eastward 9.9° to Tau (τ) Pegasi. From τ I took a brief detour 3.2° southward to take a look at yet another double star, this time Σ 3007 (6.6, 9.9; 5.9"; 91°), a challenging pair of deep yellow and white stars of unequal magnitude separated by less than 6". Returning to τ, sweep 2.2° north to 6th magnitude SAO 91217 and then eastward 4.8° to NGC 7741. This face-on barred-spiral galaxy has a pretty low surface brightness and hides in the glow of a nearly superimposed 9th-magnitude star. At 30x, this object is barely detectable as a featureless faint fuzzy wisp to the south of the 9th-magnitude star. At a magnification of 60x, NGC 7741 becomes a little easier to see but it is still a pale gray ghost which likes to play hide-and-seek behind its companion star. High magnification (120x) puts an end to this little game and an elongated nucleus (east to west) may be glimpsed in a faint oval halo elongated north to south. At times I fancied I could glimpse a slight brightening around the perimeter of the halo, which, when combined with the central bar gave the strong impression of a spectral Θ floating in the darkness. This galaxy is rife with active star-forming regions, both in the bar and in the spiral arms. Professional studies of NGC 7741 have revealed ten resolvable knots along the central bar, at least eight of which are known to reside within the bar itself. These knots are bright young star clusters and OB associations. Researchers Martin and Friedli provide an excellent high-resolution image of NGC 7741's central bar in their 1997 paper published in Astronomy & Astrophysics. There is evidence for considerable dust along the central bar and any nucleus this galaxy may possess is completely obscured from our view (Phillips, 1996). The brightest stars in this galaxy have a blue magnitude of about 21.5. The largest HII region (actually two regions superimposed upon one another) has an angular extent of about 3" (Sandage 1994). NGC 7741 lies at an estimated distance of 44 million light years (Strong & Sinnott, 2000).
NGC 16 (H.IV.15): This galaxy lies 1.5° north and 5.5° east of NGC 7741. It is also only 1.4° south of Alpha (α) Andromedae, so it may be located that way as well. Small and faint, NGC 16 is a challenge to spot at low magnifications. At 30x I was able to detect little more than a small fuzzy patch of light. At 60x this fuzzy patch appears elongated northeast to southwest with a hint of a brighter center. The view at 120x is much the same, an elongated halo of light with a somewhat brighter center floating in a field sprinkled with a couple dozen faint stars. The professional literature has very little to say about NGC 16. Sandage notes a central bar that is nearly perpendicular to the major axis of the faint outer envelope (Sandage, 1994). The faint barred spiral NGC 22 lies 11.5' to the northwest, sharing the same field of view. I was unable to detect this object, but those with larger instruments may have a shot at it. NGC 16 lies 140 million light-years away from Earth (Strong & Sinnott, 2000).
NGC 23 (H.III.147): This galaxy is located 1.8° south of NGC 16; a 9th magnitude star lies about 12' away to the northwest, the brightest object in an otherwise dim star field at 30x. The galaxy itself is faintly visible as a roughly circular patch of featureless haze. Bumping the magnification up to 60x this low-surface brightness object appears to be elongated northwest to southeast with a marginally brighter center. The southeastern end is brighter than the northwestern. At high magnification (120x) the source of this brightening is revealed to be a faint foreground star (possibly two). A very faint halo surrounds the brighter central regions. A companion galaxy, NGC 26, located 9.2' away to the southeast, is faintly visible with averted vision as a small, faint, circular patch of light. Morphologically, this galaxy is thought to belong to a subclass of the Hubble-type Sb galaxies of which NGC 210 in Cetus is the prototype. Galaxies in this class possess two sets of spiral arms, a tightly wound inner set and a loosely wound outer set. A supernova was discovered in this galaxy in 1955 on a plate taken with the 200-inch telescope at Palomar (Sandage, 1961). NGC 23 lies at the rather remarkable distance of 210 million light years (Strong & Sinnott, 2000).
We will conclude this session with a brief look at a few more double stars. Σ 24 (7.6, 8.4; 5.2"; 248°) is located 1.9° east and a little north of NGC 23. This bluish-white and white pair is best seen with high magnifications due to its small angular separation. 55 Piscium (5.4, 8.7; 6.5"; 194°), located 6.8° southeast of Σ 24, is challenging because the magnitude difference between the components and their small angular separation. At 240x I was able to obtain a nice view of the yellow and blue pair. 65 Piscium (6.3, 6.3; 4.4"; 297°), located 6.4° north and 2.2° east of 55, is a fine pair of yellowish-white stars, which are much easier to resolve than the previous two objects in spite of the small angular separation because of their equal brightness. At 240x they look like a distant pair of headlights. 36 Andromedae (6.0, 6.4; 0.9"; 313°), located 4.1° south and 1.2° east of 65 Psc and just west of Eta (η) Andromedae, is a pretty severe test of resolution for a 6-inch scope. At 240x the stars appeared peanut-shaped with a slight notch between them but no dark sky indicative of true resolution. For our final object, we'll dial down the magnification to 30x in order to better appreciate the "splendid low power field" mentioned by James Muirden surrounding the double star Psi-1 (ψ¹) Piscium (5.6, 5.8; 30.0"; 159°), located 2.2° south and 1.9° east of 36 And. Views like this one remind us that not every sight worth seeing in the night sky is going to be found on a list of deep-sky wonders….
REFERENCES & ADDITIONAL READING
Boffi, F. R., W. B. Sparks, and F. D. Macchetto. 1999. A search for candidate light echoes: Photometry of supernova environments. Astronomy & Astrophysics Supplement Series. 138:253-266.
de Jong, R. S. 1996. Near-infrared and optical broadband surface photometry of 86 face-on disk dominated galaxies. II. A two-dimensional method to determine bulge and disk parameters. Astronomy & Astrophysics Supplement Series. 118:557-573.
Houston, Walter Scott, Stephen James O'Meara (editor). 1999. Deep-Sky Wonders. Sky Publishing Corp. Cambridge Massachusetts.
Kepple, George Robert and Glen W. Sanner. 1998. The Night Sky Observer's Guide. Vol 1. Willmann-Bell, Inc. Richmond, Virginia.
Luginbuhl, Christian B. and Brian A. Skiff. 1989. Observing Handbook and Catalogue of Deep-Sky Objects. Cambridge University Press, Cambridge, United Kingdom.
Martin, P., and D. Friedli. 1997. Star formation in bar environments. I. Morphology, star formation rates and general properties. Astronomy and Astrophysics. 326:449-464.
Michard, R., and J. Marchal. 1994. Quantitative morphology of E-S0 galaxies. III. Coded and parametric description of 108 galaxies in a complete sample. Astronomy & Astrophysics Supplement Series. 105:481-501.
Muirden, James. 1983. The Amateur Astronomer's Handbook. 3rd Ed. Harper & Row, Publishers. New York, New York.
Phillips, Andrew C., et al. 1996. Nuclei of Nearby Disk Galaxies. I. A Hubble Space Telescope Imaging Survey. The Astronomical Journal. 111:4:1566-1574.
Polakis, Tom. 2001. Observer's Log: A Sampling of Edge-on Galaxies. Sky & Telescope. 102:5:122-124.
Sandage, A. 1961. The Hubble Atlas of Galaxies. Washington, D.C.: Carnegie Institution of Washington.
Sandage, A., and J. Bedke. 1994. The Carnegie Atlas of Galaxies. Volume 1. Carnegie Institution of Washington.
Strong, Robert A. and Roger W. Sinnott. 2000. Sky Atlas 2000.0 Companion, 2nd Ed. Sky Publishing Corp. Cambridge Massachusetts.
This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.