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Collinder 328, Melotte 170, NGC 6352

Proper NameNone
Caldwell NumberC81
NGC/IC NumberNGC 6352
Other DesignationsCollinder 328, Melotte 170
Right Ascension17h 25m 29s
Declination-48° 25' 20"
Distancec.18,300 light years
c.5,600 parsecs
MagnitudeApparent: +7.96
Absolute: -5.79
DiameterApparent: 9'
Actual: 48 light years
Optimum VisibilityJune / July (Usually visible from southern latitudes)

This globular cluster in Ara lies on the edge of the Milky Way in the sky, whch means that it falls relatively close to the disc of the Milky Way Galaxy (though given the cluster's great distance, 'close' in this context means approximately 1,600 light years). The cluster is some 18,300 light years from the Sun, and it lies very approximately in the direction of the Galaxy's core, some 13,000 light years beyond the cluster.

Imagery provided by Aladin sky atlas

As is typical for globular clusters, C81 is immensely old, with an estimated age of some 12.7 billion years. Its stars are spread in an unusually loose pattern for a cluster of this kind. On the Shapley-Sawyer scale, which measures globular cluster concentration from I (densely concentrated toward to the centre) to XII (barely any detectable concentration), C81 rates as class XI.


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