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NGC 6934

One of two prominent globular clusters within the small constellation of Delphinus the Dolphin, with the other being C42 or NGC 7006, somewhat to the north and east. C47 lies in the more southerly parts of Delphinus, and following the Dolphin's tail southwards leads to this shining ball of stars. With a visual magnitude of +8.8, the cluster is too faint to be seen without optical aid.

Lying on the fringes of the Milky Way, C42 lies against a very rich starfield. It is also on an almost direct line of sight with the orange star BD +06 4572, which appears in photographs of the cluster to lie within its outer halo, but in fact falls in the very near foreground. The star is about 160 light years from the Sun, while the cluster is estimated to lie at a distance of some 51,200 light years (that is, more than three hundred times farther than its orange foreground star, which it nonetheless appears to dwarf in the sky).

The cluster comprises a relatively loose globe composed of several thousand stars, which is thought to possess a total mass approaching 300,000 times that of the Sun. It follows a highly eccentric and steeply inclined orbit around the Milky Way Galaxy. Similarities of structure and orbit suggest that C47 may share an origin with another globular cluster, NGC 5466 in Boötes, though the two clusters are now spread far apart across the Galaxy.


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