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M15

 

M15

 

This globular cluster is among the more conspicuous ones on the northern sky, having bright stars with an apparent brightness of about 13 mag. Its angular diameter is about 7 arcminutes visually and 12.3 arcminutes photographically. The distance of this cluster has been measured to be approximately 33,600 light years.

M15 is probably the densest globular star cluster in the Milky Way galaxy, because its core has undergone a so-called "core collapse", a concentration of the central component, which is common in the dynamical evolution of globular clusters. The central core is extremely small, only about 8.4 arcseconds in diameter, corresponding to a linear extent of roughly 1.4 light years. M15 is a candidate to hold a Black Hole at its very center.

M15 was the first globular cluster in which a planetary nebula, Pease 1, could be identified (Pease 1928, on photographic plates taken at Mt. Wilson in 1927). Pease 1 is one of only four known planetary nebulae in Milky Way globular clusters.

M15 was discovered by Jean-Dominique Maraldi in 1746. William Herschel was the first to resolve the cluster into individual stars in 1783.


Exposure Data


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© 2010 Wolfgang Howurek