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NGC 6694

The small constellation of Scutum, the Shield, lies on the band of the Milky Way as it stretches out northward from the heart of the Galaxy in Sagittarius. It is home to two open clusters in the Messier Catalogue: M11, the Wild Duck Cluster, and this cluster, M26. The Wild Duck Cluster lies on the edge of naked eye visibility, while M26 - to the approximate southwest - is rather fainter, and cannot be resolved without optical aid. Though the fainter of the two, M26 is actually somewhat nearer to the Solar System, at a distance of about 5,200 light years (some thousand light years closer than the Wild Duck).

There are about ninety stars in the M26 cluster, occupying a region fo space some 22 light years across. The cluster exhibits one significant pecularity: unlike most open clusters, its stars seem to be denser in its outer regions, and less tightly clustered in its centre. The reason for this is unclear, with the simplest explanation being that an intervening zone of dark matertial lies between the Sun and the cluster, obscuring its central stars from view. This explanation is not certain, however, and it is possible that M26 actually does have a sparse core with stars concentrated instead in its outer reaches.


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