TheWild Duck Cluster (also known asMessier 11, orNGC 6705) is anopen cluster of stars in theconstellationScutum (the Shield). It was discovered byGottfried Kirch in 1681.[3]Charles Messier included it in his catalogue of diffuse objects in 1764. Its popular name derives from the brighter stars forming a triangle which could resemble a flying flock ofducks[3] (or, from other angles, one swimming duck). The cluster is located just to the east of the Scutum Star Cloud midpoint.[7]
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 about 316 million years.[5] The core radius is 1.23 pc (4.0 ly) while thetidal radius is 29 pc (95 ly). Estimates for the cluster's mass range from3,700 M☉[8] to11,000 M☉,[4] depending on the method chosen. The brightest cluster member is visual magnitude 8, and it has 870 members of at least magnitude 16.5. It has an integratedabsolute magnitude of –6.5, and a visualextinction of 1.3.[7]
The cluster ismetal-rich with an iron abundance of [Fe/H] =0.17±0.04. Despite its youth, it shows an enhancement ofalpha process elements. Possibly this is due to an enhancement of its birthmolecular cloud by a nearbyType II supernova explosion.[5] At least ninevariable star members have been identified with high probability, plus 29 lower probability members. The former include twoeclipsing binary star systems.[9] The cluster is located 6.8 kpc (22,000 ly) from theGalactic Center, close to thegalactic plane, and is not far from its birthplace.[5]
![A portion of M11, imaged by the Hubble Space Telescope[10]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aWild_cosmic_ducks_Messier_11.jpg)
