The Wild Duck Cluster in Scutum, catalogued as Messier 11 or NGC 6705, is one of the richest and most compact open clusters in the sky.
M 11 was discovered by the German astronomer Gottfried Kirch in 1681, and first resolved into stars by William Derham around 1733. Charles Messier included it in his catalog in 1764. The Wild Duck cluster's common name comes from Admiral Smyth, who noted that its fan-shaped appearance resembles "a flight of wild ducks."
The Wild Duck Cluster is 14' in diameter, about 1/3 the size of the full moon. With a total magnitude of 6.3, it is visible in binoculars. With an 8-inch telescope at low power, it is a remarkable object. M 11 contains an estimated 2900 stars, about 500 of which are brighter than magnitude 14. The cluster's stars are distributed in a network of knots and clumps, mixed with some meandering dark lanes. The two most conspicuous of these wind from the cluster's center to its northern and western edges. Although difficult to discern among the profusion of stars, careful scrutiny shows the east-pointing V of the brighter cluster stars.
The Wild Duck Cluster is one of the richest and most compact open clusters. Messier 11 is so rich that it resembles the looser globular clusters, but it is in fact an intermediate-age open cluster, 250 million years old. It is extremely luminous for a somewhat evolved open cluster, with an absolute magnitude of -6.9, a luminosity of 48,000 suns. It is about 6,000 light years away, and receding at 22 km/sec.