Small Wonders: Scutum 1/16

Small Wonders: Scutum A monthly sky guide for the beginning to intermediate amateur astronomer Tom Trusock 22-July-2007

Figure 1: W idefield map

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Figure 2: W idefield image courtesy Bert Van Donkelaar For a full resolution image w/ a sky map superimposed, see ”Additional Resources‘ at the end of this article.

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Target List Name Type Size Mag RA DEC B110 Dark Nebula 9.0’ 18h 50m 37.8s -04 45’ 31” B111,119a Dark Nebula 120.0’ 18h 51m 25.8s -04 59’ 30” B114-8 Dark Nebula 50.0’x5.0’ 18h 53m 38.2s -07 05’ 29” Basel 1 Open Cluster 9.0’ 8.9 18h 48m 38.0s -05 50’ 32” IC 1295 Planetary Nebula 1.5’ 15 18h 55m 03.6s -08 49’ 03” M 11 Open Cluster 11.0’ 5.8 18h 51m 32.0s -06 15’ 30” M 26 Open Cluster 10.0’ 8 18h 45m 44.6s -09 22’ 25” NGC 6664 Open Cluster 12.0’ 7.8 18h 36m 56.4s -08 10’ 41” NGC 6712 Globular Cluster 9.8’ 8.1 18h 53m 30.8s -08 41’ 49” R Scuti Star 5.4 18h 47m 54.9s -05 41’ 52”

Challenge Objects Name Type Size Mag RA DEC PK 20-0.1 (Abell 45) Planetary Nebula 5.0’x4.7’ 12.9 18h 30m 45.0s -11 36’ 45” PK 27-3.1 (Abell 49) Planetary Nebula 35”x33” 16.1 18h 53m 56.1s -06 28’ 29”

Scutum cutum, formerly Scutum Sobiescianum, is an interesting little constellation. With only one star brighter than 4th magnitude, it‘s something of a cosmic Rorschach test, then it‘s the only Sp olitical constellation still found in the night sky, and finally with it‘s location in summer Milky Way, Scutum‘s small size belies a fairly large number of interesting targets. Johannes Hevelinus introduced Scutum Sobiescianum (Sobieski‘s Shield) in 1690, to honor King Jan III Sobieski of Poland. King Sobieski‘s greatest moment came in 1683 during the battle of Vi- enna, with nothing less than European civilization at stake. At 4am on September 12, 1683 Sobi- eski found his 81,000 Polish, Austrian and German troops arrayed against 130,000 Turks. Out- numbered, they fought throughout the day, till 5pm when King John led a cavalry group against the enemy, breaking their battle line and scattering them in confusion. A mere 30 minutes later, he entered the tent of the enemy commander and the battle was over. Thereafter he was hailed by the Pope and other noteables as the —Savior of Vienna and Western European Civilization“. King John died on June 17, 1696. Contrary to the lines and drawings we see in the star atlases, I find there‘s really no easily recog- nizable figure in Scutum. Overshadowed by its neighbors Aquila, Sagittarius and Serpens, the easiest way to find it is to simply scan the Milky Way between Sagittarius and Aquila – you can use the three stars at the tip of Aquila as a guide. Scutum‘s brightest star (Alpha) rings in at a rather paltry magitude 3.85, but as mentioned above don‘t let that fool you. Because it‘s embed- ded in the summer Milky Way there are a number of interesting targets.

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Figure 3: Scutum finder chart For example, within this small space the catalogs in SkyTools 2 list 52 planetary nebula, 21 open clusters, 91 dark nebulae, 3 diffuse nebulae, and one globular cluster. Before hauling out that telescope though, I‘d recommend a few observations using the old mark 1 eyeball and a decent set of binoculars. The first thing you‘ll notice is the great Scutum star clouds. Being on the edge of the great rift in the Milky Way helps the star clouds to stand out, but there are simply a boatload of stars in this region regardless. On those warm summer nights, I like to trace the Milky Way with my naked eye every few min- utes during late dusk. I find it interesting to watch our galaxy grow. Over the years, I‘ve at- tempted a sketch of the Milky Way, but each night I try it winds up looking just a little bit differ- ent.Watching it emerge from dusk treats me to a similar view over the course of one evening.

R Scuti Speaking of stars, while you‘re in the area, you should take a gander at R Scuti. This is a member of the RV Tauri class of pulsating variable stars and ranges from magnitude 4.9 to 8.2 over its 140 day period (although the deep minimum appears only every fourth or fifth cycle). This ancient variable is located between two of our galaxy‘s spiral arms: our own Orion arm, and the Sagitta- rius-Carina arm.

Dark Nebulae in Scutum Crossen, in —Binocular Astronomy“ notes that there are two great star clouds in Scutum, one in the southwest corner of the constellation, and the other in the northeast. From a dark site, these are easily visible to the naked eye, and come to life in binoculars or a rich field telescope (if you‘re using a telescope, pop in your lowest power eyepiece and be sure to look through it while moving it to scan the area to better make note of the —boundaries“ of the star clouds). My eyes are often shocked by the sheer number of stars in the area, and as I let my vision wander, I often forget to

Tom Trusock 22-July-2007 Small Wonders: Scutum 5/16 use averted vision. Remember to do so, and take a few minutes to study the area carefully. You‘ll note vast regions of darkness scattered throughout the starry background. Scutum is rife with dark nebulae. These concentrations of gas and dust block the light of distant stars and create a —hole in space“ effect. To me, the largest and most noticeable of these holes (B111, 119a) lies just to the north of Messier 11 and creates the illusion of a stellar no man‘s land.

Figure 4: Scutum Area Map 1

B114-8 A degree to the SE of Messier 11, we find B114-8. Eric Graff has contributed a won- derful sketch of this area. Author Steve Coe has compiled a docu- ment listing the best of these holes in space and has posted on the SAC‘s web- site. See The Best of Barnard‘s Dark Nebulae. Steve lists 5 in Scutum alone. For dark nebulae, I‘ve found I need to use low powers, wide fields and averted vision. Some are obvious, but others require a careful attention to detail. The best in- struments to see them in are probably bin- oculars or wide field refractors so as to get a good contrast with the surrounding area.

Figure 5: B114/115 sketch courtesy Eric Graff 22-July-2007 Tom Trusock 6/16 Small Wonders: Scutum

M11 — The Wild Duck Cluster And now, on to the —standard“ deep space targets. Let‘s start with what‘s likely the most viewed object in Scutum – Messier 11, the Wild Duck Cluster. When I asked for observations of targets in Scutum, this one object, by itself claimed over half of the total received, and talk about an overwhelming response! I want to thank everyone for submitting their images, obser- vations and sketches. Unfortunately, I‘m not able to use all of the, but there were a num- ber of excellent ones.

Figure 6: M11 (DSS)

Figure 7: M11 Image Courtesy Michael Fulbright

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Figure 8: M11 Sketch Courtesy Carlos E Hernandez Just visible to the naked eye, this cluster seems to be (visually anyway) one of the densest open clusters in the night sky. With a very small telescope or binoculars it‘s easily mistaken for a globu- lar. But with moderate magnification anything above 2-3 inches or so will resolve it clear across the face. In 1844 Admiral Smyth compared it to a —Flight of Wild Ducks“ and thus it earned the name —Wild Duck Cluster“. Confused astronomers have been looking for the ducks ever since. Sue French clears up the mystery in her excellent Celestial Sampler by including a copy of Smyth‘s sketch that accompanied his observation. The flight of ducks can be seen to be a long flat V off to one side. Personally I see an arrowhead or angelfish in this most populous open cluster. What do you make out? Note the one star that seems to pop out in from the cluster itself? Many people suspect it‘s actu- ally a foreground object.

22-July-2007 Tom Trusock 8/16 Small Wonders: Scutum Basel 1 While you‘re in the area, you might take a quick look just under a degree to the NW for Basel 1. Eric Graff has this to say about the region while contributing the following sketch: The Wild Duck Cluster, M11 is a truly spectacular object in an amazing field. It seems to rest on an island in a sea of dark nebulosity. Nearly a degree away to the northwest look for the scrappy little open cluster Basel 1 and its odd little ring of six faint stars.

Figure 9: Basel 1 Sketch Courtesty Eric Graff

Tom Trusock 22-July-2007 Small Wonders: Scutum 9/16 NGC 6712 and IC 1295

Figure 10: Scutum Area Map 2

Figure 11: NGC 6712 (DSS) Figure 12: IC 1295 (DSS) Now drop about 2.5 degrees almost directly south of M11 for a surprisingly bright globular cluster. Given that Messier included M26 in his catalog (which we‘ll look at in a moment), I‘m almost shocked that he managed to overlook this little gem. I effortlessly picked it out from the starry background in a 6“ f/6 achromat at 23x. At 100x, I believe I began to see some resolution of the globular, but given its background setting in the Milky Way I can‘t be 100% certain. NGC 6712 is fairly small for a globular cluster, but it‘s also rather close to us in space – at least compared to other globulars. Its orbit around the galaxy takes it to within a mere 1000 light years of the galactic center, and just completed a passage through the galactic plane a few million years ago. Perhaps as a result, astronomers have found evidence that the cluster is ”evaporating‘ – loosing stars to the galactic halo.

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Figure 13: NGC 6712 image courtesy ESO NGC 6712 rates as Hidden Treasure #95 in Stephen James O‘Meara‘s excellent and highly rec- ommended tome: —Hidden Treasures“. In the first edition of his book, O‘Meara also mentions a nearby planetary nebula (although he mislabels the planetary IC 129). The planetary IC 1295 lies only .25 degrees from NGC 6712 and is easily visible in the same field of view in nearly any tele- scope. IC 1295 is just under ² the diameter of NGC 6712. In the six inch refractor, at 100 power, I can only glimpse the barest outline of the planetary using averted vision – while I do see an entire disk, the brighter segment along the edge pops out a bit better. A UHC filter hardly improves the view over the naturally aspirated version, while the use of an OIII filter causes a dramatic difference and the planetary springs into view. At a recent star party, a group of friends and I had occasion to examine this pairing in several dif- ferent telescopes. Although the globular was obvious in a 5“ apo at 45x, the planetary was all but invisible until we used an OIII filter. Under the filter the planetary popped out – easily with averted vision, but still visible with direct. We also took a peek at this grouping with a couple of different SCT‘s – 10 and 11 inchers. In the 11“ SCT, the planetary was clearly visible without a filter, and the globular showed excellent resolution. They were barely framed in the wide field of a 17mm Nagler – lower power was a bit better. To view them at the same time, a 31 Nagler was used in concert with an OIII filter in the 10“. This didn‘t reveal as much detail or resolution as the 17 or 20 did in the 11 inch SCT, but provided a great view none the less. The best view of the planetary came in the 11 incher using a 20mm Nagler with an OIII filter. Round, clearly defined with bright edges and an offset darker interior hole, this planetary is worth some serious study. Later in the evening, I had a chance to look for the globular with a set of 12x36 IS binos, and it stood out from the background surprisingly well. Rather unshockingly, there was no hint of the planetary. Mark Shapiro writes: In my 12“ telescope, I was able to observe NGC 6712 using a 21mm Stratus at 71X and 13mm Stratus at 115X; but the real object of the exercise was to find nearby IC 1295. Af- fixing a Lumicon UHC filter, the planetary nebula became readily apparent as a ghostly roundish donut.

Tom Trusock 22-July-2007 Small Wonders: Scutum 11/16 M 26 Now scan two degrees WSW for the other Messier object in Scutum – M26.

Figure 14: M26 (DSS) Don‘t confuse Messier – M26 with that other M26 – the Pershing Tank. One definitely commands your attention, while the other – well... It depends on the aperture, but it‘s undoubtedly over- shadowed by M11. In my 4“ scope, M26 is rather unimpressive revealing just around a dozen stars. In a 6“, I count maybe 18 stars, and the count goes up from here as aperture increases. In lar- Figure 15: M26 Sketch ger apertures, this is a beautiful and sur- Contributed by Vedran Vrhovac prisingly dense open cluster.

Figure 16: M26 Image Courtesty John Crilly

22-July-2007 Tom Trusock 12/16 Small Wonders: Scutum NGC 6664 Our final stop on the regular tour this evening is NGC 6664. Just off Alpha Scuti, 2.5 degrees WNW of M26, we find a nice little open cluster not nearly as tight or dense as M26, but a fair bit brighter. In the 6“ tele- scope, my mind persists in seeing a rather distinct M here (I‘m not nearly as imaginative as Mark it seems – see the following quote), and I count around two dozen members in the cluster. One thing numerous obsevers have commented on but I have yet to note, are areas of low stellar density across the face. Are these real? Or simply the effect of the mind wanting to organize random bits of

data? What do you see? Figure 17: NGC 6664 (DSS) Mark Shapiro writes: This is one of those clusters more remarkable for its proximity to a bright star than for its intrisic attributes. Being near Alpha Scuti, it is easy to find. On 7/12/07, under some of the very best July seeing conditions here in the northeast, I observed it with the 40mm Para- gon at 38X in my 12“. The very wide field gave an incredibly strong impression of a jelly- fish swimming pulsatingly away from Alpha Scuti.

Challenge Objects Tonight I‘ve got two Abell Planetaries for you. The Abell Planetaries were cataloged by George Abell in the 1950‘s using DSS (Deep Sky Survey) plates. The original Abell catalog had 86 entries – 5 of which were determined to be spurious. Abell 11 is most likely a reflection nebula, 17 is nonexistent, 32 is most likely a fault in the plate exposure, 76 is a ring galaxy, and 85 is apparently a supernova remnant. Tonight we‘ll see if we can find 45 and 49.

Abell 45 — PK 20-0.1

Figure 18: Abell 45 DSS image

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Figure 19: Abell 45 Finder Chart

Figure 20: Abell 45 Supplementary Chart

22-July-2007 Tom Trusock 14/16 Small Wonders: Scutum Abell 49 — PK 27-3.1

Figure 21: Abell 49 Finder Chart

Figure 22: Abell 49 Supplementary Chart

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Figure 23: Abell 45 DSS Image As nearly always, for these you‘ll require aperture, good maps, an abundance of patience and (in this particular case) an OIII filter. Those interested in viewing more of the Abell Planetary Nebulae should pick up a copy of Alvin Huey‘s The Abell Planetary Observer‘s Guide. And with that, that‘s it for this month. Once again, thanks to the readers who submitted observa- tions, sketches and photos, there were far more excellent submissions this month than I could use. Your contributions greatly enrich these articles. As always, I‘m gratified if folks find my meanderings useful.

Till next time œ

-Tom

BTW - Tip for a happy home #23487: Don‘t let your wife catch you googling for MASTDSS. It should be MAST DSS. Note the space.

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Additional Resources / References / Just Plain Cool Stuff o Steve Coe: The Best of Barnard‘s Dark Nebulae http://www.saguaroastro.org/content/Best-of-Barnards-Dark-Nebulae.htm o Alvin Huey: Observing Guides (Abells, Hicksons and Arps) http://www.faintfuzzies.com/ObservingGuidebooks.htm o Stephen James O‘Meara: Hidden Treasures o Very Large Telescope Observations of the Peculiar Globular Cluster NGC 6712: Discovery of a UV, H
-Excess Star in the Core http://www.journals.uchicago.edu/ApJ/journal/issues/ApJL/v542n1/005491/005491.html o Bert Van Donkelaar‘s W idefield Scutum Image: o Full resolution widefield image http://users.bigpond.net.au/avandonk/SCUTUM_M11.jpg o Full resolution widefield image with superimposed map http://users.bigpond.net.au/avandonk/MAP.jpg

If you liked this article, you may want to check out the rest of the series. I‘d love to hear of your experiences under the night sky – please feel free to e-mail me or send any observing reports to: [email protected] Please indicate if I can cite your observations in future columns. Photographic Images Courtesy DSS (except where noted): copyright notice http://archive.stsci.edu/dss/acknowledging.html Star Charts Courtesy Chris Marriott, SkyMap Pro 10 Printed with Permission http://www.skymap.com Locational Images Courtesy Bill Tschumy, W here is M13? Used with Permission http://www.thinkastronomy.com/

Special Thanks to Olivier Biot for assistance with the PDFs and all those who take the time to read and contribute to this series.

Tom Trusock 22-July-2007