NGC 6440 is a globular cluster of stars in the southern constellation of Sagittarius. It discovered by German-English astronomer William Herschel on 28 May 1786. With has an apparent visual magnitude of 9.3 and an angular diameter of 4.4′, it can be viewed as a fuzzy blob in a small telescope.[4] Its Shapley–Sawyer Concentration Class is V.[1]
This cluster is located at a distance of 27.1 ± 1.3 kly (8.3 ± 0.4 kpc) from the Sun.[3] It is situated toward the galactic bulge of the Milky Way,[3] about 26 kly (8.0 kpc) from the galactic center. The center of the cluster is fairly concentrated but does not appear to have undergone a core collapse.[7] It has a core radius of 0.85 ly (0.26 pc) and a half-mass radius of 6.6 ly (2.02 pc). Observations suggest it is one of the most metal–rich globular clusters in the galaxy and it is close to solar metallicity.[3] NGC 6440 is a rich target for Astrophysical X-ray sources. As of 2022[update], thirteen pulsars have been discovered in NGC 6440.[3]
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