The Wild Duck Cluster (Messier 11, or NGC 6705) is an open cluster of stars in the constellation Scutum (the Shield). It was discovered by Gottfried Kirch in 1681. Charles Messier included it in his catalog of diffuse objects in 1764. Its popular name derives from the brighter stars forming a triangle, which could resemble a flying flock of ducks (or, from other angles, one swimming duck). The cluster is located just east of the Scutum Star Cloud midpoint.
The Wild Duck Cluster is one of the richest and most compact of the known open clusters. It is one of the most massive open clusters known, and it has been extensively studied. Its age has been estimated to be about 316 million years. The core radius is 1.23 pc (4.0 ly), while the tidal radius is 29 pc (95 ly). Estimates for the cluster’s mass range from 3,700 M☉ to 11,000 M☉, depending on the method chosen. The brightest cluster member is visual magnitude 8, with 870 members of at least magnitude 16.5. It has an integrated absolute magnitude of –6.5 and a visual extinction of 1.3.
