Aquila wide-SQ

Scoping Scutum

This small constellation lays claim to the impressive Scutum Star Cloud.

The little constellation Scutum is found in the Milky Way south of Aquila, the Eagle. (Gary Seronik)

A perfectly rectangular constellation only 12 by 9 degrees in extent, Scutum (SKEW tum) is squeezed between two giant neighbours: Aquila to the northeast and Sagittarius to the south. The glittering Milky Way widens as it crosses these groups and simply overwhelms the shield’s nondescript star pattern. In fact, it is the brightest discrete patch of Milky Way outside Sagittarius in the northern sky.

That patch is the Scutum Star Cloud, which nearly fills Scutum’s northeast quadrant. From a rural observing site, my 8×56 binoculars show the star cloud spreading from fifth magnitude epsilon (ε) Scuti to fourth-magnitude beta (β), almost four degrees to the north. The cloud is wedge-shaped; its eastern flank blends smoothly into the Milky Way, but its western and northern edges are sharp. Trending northeastward across the cloud is a two-degree-long chain of six or so sixth- and seventh-magnitude stars that opens into a quadrangle roughly ½ by ¼ degrees in extent. My vivid imagination morphs this lanky asterism into an upside-down golf club whose head swings toward a grainy “golf ball” called Messier 11 (M11), on the cloud’s northeast corner. If you identify the golf club in binoculars, you are in the middle of the Scutum Star Cloud.

LeDrew-Scutum chart
Easy to overlook, the tiny, dim constellation Scutum is home to a star-rich chunk of the summer Milky Way. It also contains M11, one of the most impressive star clusters visible in a small telescope. Finding it is easy using the bottom stars of Aquila as a guide. (Cartography by Glenn LeDrew)

The prize of Scutum is M11, a stunningly rich sixth-magnitude open star cluster 6,000 light-years from Earth. Although it is less than ¼ degree wide, M11 is packed with 700 suns 11th magnitude and dimmer. An 8.5-magnitude star — likely in the foreground gleams like a midcluster nova, while a ninth-magnitude pairing shines prettily near the cluster’s southeastern outskirts. The compact blaze of M11 is an alluring study in a typical backyard telescope, even when viewed in fairly serious light pollution. In my city based 4¼-inch Newtonian reflector at 22×, M11 is only a textured haze around the glaring foreground star. But upping to 54× resolves the haze into faint specks fanning northwestward. The “nova” gleams southeast of centre, near the apex of the fan. More magnification pulls in more specks. At 93×, the cluster seems unevenly illuminated and slightly squarish.

In 1844, retired British admiral (and active stargazer) William Smyth wrote that M11 “somewhat resembles a flight of wild ducks” in V-formation. Smyth’s evocative description led to M11’s being dubbed the Wild Duck Cluster. Begging the admiral’s pardon, but I don’t see your celestial flock of flyers. My larger backyard scope, a 10-inch Dobsonian, strengthens my perception of M11 as a “squarish” powder of pinpoints. At 116×, the cluster displays four fairly straight sides with a few short rows inside. To my eye, the boxlike pattern of bright lines and dark lanes suggests an aerial view of a small garden maze. This harmless hallucination (hey, it’s no worse than wild ducks!) is supported by Vernon, British Columbia, ob­server John Karlsson’s back­yard sketch of M11, using an 8-inch reflector telescope, that portrays a square-sided structure. The Garden Maze Cluster, anyone?

Easily visible in binoculars, but even more impressive telescopically, M11 is 5,600 light-years distant—a lovely collection of stellar points, shown here as seen through an 8-inch Newtonian telescope. (Sketch by John Karlsson)

The 1.8 degrees of sky between M11 and beta Scuti con­tain the roughly rectangular head of the golf club asterism I mentioned earlier. Mark­ing its northeast corner is Herschel VI 50, an orange 6.2-magnitude star with an 8.2-magnitude companion 111 arc seconds southward. On the southeast corner is Struve 2391, a binary with 6.5- and 9.6-magnitude components 38 arc seconds apart. The northwest corner is anchored by R Scuti, a yellowy variable that fluctuates between fifth and sixth magnitude, with occasional dips to eighth, on a timescale of weeks. When R reaches maximum, it outshines every other star in the golf club. Inside the head of the club is Basel 1, an obscure cluster that forms a clump of dim dots in my 10-inch beginning at around 100×.

Also visible along this same 1.8-degree corridor — in a pristine, dark country sky — is the abrupt boundary between the Scutum Star Cloud and Barnard 111 (B111), a large, crescent-shaped dark nebula blotting out the Milky Way. I like to aim my scope at the bottom of the glittery star cloud then, using medium magnification, sweep through the blizzard of suns into the almost starless void of B111. There, I pick up darker pockets. The blackest of these “nebulas within a nebula” are B110, ¾ degree east of beta Scuti, and B113, ½ degree north­east of B110. These are not true starless regions but more opaque clouds of cosmic dust inward toward the core of the Milky Way Galaxy. Scutum may be small, but its contrasting fields of dazzle and dark are captivating in any optics.

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