NGC 6440

NGC 6440
HST image of NGC 6440
Observation data (J2000 epoch)
ClassV[1]
ConstellationSagittarius
Right ascension17h 48m 52.67s[2]
Declination−20° 21′ 34.5″[2]
Distance27.1 ± 1.3 kly (8.3 ± 0.4 kpc)[3]
Apparent magnitude (V)9.3[4]
Apparent dimensions (V)4.4′[4]
Physical characteristics
Mass> 4.42×105[3] M☉
Metallicity = −0.56[3] dex
Estimated age≈11 Gyr[5]
Other designationsNGC 6440[6]
See also: Globular cluster, List of globular clusters

NGC 6440 is a globular cluster of stars in the southern constellation of Sagittarius. It was discovered by German-English astronomer William Herschel on 28 May 1786. With an apparent visual magnitude of 9.3 and an angular diameter of 4.4′, it can be observed as a fuzzy blob when viewed through 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, thirteen pulsars have been discovered in NGC 6440.[3]

  1. ^ a b Cite error: The named reference Shapley_Sawyer_1927 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Di_Criscienzo_et_al_2006 was invoked but never defined (see the help page).
  3. ^ a b c d e f g Cite error: The named reference Vleeschower_et_al_2022 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference O'Meara_2007 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Origlia_et_al_2008 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference simbad was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Ortolani_et_al_1994 was invoked but never defined (see the help page).