The New General Catalogue of Nebulae and Clusters of Stars (abbreviated as NGC) is a catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, known as the NGC objects. It is one of the largest comprehensive catalogues, as it includes all types of deep space objects, including galaxies, star clusters, emission nebulae and absorption nebulae.
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NGC 6535
NGC 6535 is a globular cluster of stars located at a distance of 22,200 light years from Earth in the equatorial constellation of Serpens, and is listed in the New General Catalogue. Its discovery is usually attributed to astronomer John Russell Hind in 1852. However, Wolfgang Steinicke has uncovered evidence that William Herschel's first discovery was actually NGC 6535, which he observed on 24 August 1780. This is a halo globular cluster located close to the galactic bulge at a distance of 13 kly (3.9 kpc) from the Galactic Center. It has an estimated age of 12.75 billion years. For a object of its type, NGC 6535 has a relatively low mass of 2.2×104 times the mass of the Sun. The core radius is 2.3 ly (0.71 pc) and the tidal radius is 50 ly (15.3 pc). It has an unusually high mass-to-light ratio of 11. The cluster is suspected to harbour an intermediate-mass black hole in its center. Unusually for a low-mass globular cluster, it has multiple generations of stars. Rather small and sparse for a globular cluster, this cluster contains no known RR Lyrae variables, which is unusual for a globular cluster. Nine blue stragglers have been discovered.
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Wikipedia Page: NGC 6535
NGC 6535 at In-The-Sky website