| NGC 6440 | |
|---|---|
 HST image of NGC 6440 | |
| Observation data (J2000 epoch) | |
| Class | V[1] |
| Constellation | Sagittarius |
| Right ascension | 17h 48m 52.67s[2] |
| Declination | −20° 21′ 34.5″[2] |
| Distance | 27.1 ± 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 | [Fe/H] = −0.56[3] dex |
| Estimated age | ≈11 Gyr[5] |
| Other designations | NGC 6440[6] |
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[update], thirteen pulsars have been discovered in NGC 6440.[3]
References
- ^ a b Shapley, Harlow; Sawyer, Helen B. (August 1927). "A Classification of Globular Clusters". Harvard College Observatory Bulletin. 849: 11–14. Bibcode:1927BHarO.849...11S.
- ^ a b Di Criscienzo, M.; et al. (February 2006). "RR Lyrae-based calibration of the Globular Cluster Luminosity Function". Monthly Notices of the Royal Astronomical Society. 365 (4): 1357–1366. arXiv:astro-ph/0511128. Bibcode:2006MNRAS.365.1357D. doi:10.1111/j.1365-2966.2005.09819.x. S2CID 17838243.
- ^ a b c d e f g Vleeschower, L.; et al. (June 2022). "Discoveries and timing of pulsars in NGC 6440". Monthly Notices of the Royal Astronomical Society. 513 (1): 1386–1399. arXiv:2204.00086. Bibcode:2022MNRAS.513.1386V. doi:10.1093/mnras/stac921.
- ^ a b c O'Meara, Stephen James (2007). Herschel 400 Observing Guide. Cambridge University Press. p. 233. ISBN 9780521858939.
- ^ Origlia, L.; et al. (November 2008). "Probing the Galactic Bulge with Deep Adaptive Optics Imaging: The Age of NGC 6440". The Astrophysical Journal Letters. 687 (2): L79–L82. arXiv:0809.3939. Bibcode:2008ApJ...687L..79O. doi:10.1086/593351.
- ^ "NGC 6440". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 January 2017.
- ^ Ortolani, S.; et al. (December 1994). "The low galactic latitude metal-rich globular cluster NGC 6440". Astronomy and Astrophysics Supplement. 108: 653–659. Bibcode:1994A&AS..108..653O.
External links
Media related to NGC 6440 at Wikimedia Commons- "Star-studded cluster (NGC 6440 NIRCam wide-field image)". ESA. Retrieved 2024-08-20.
- Frommert, Hartmut. "NGC 6440". Students for the Exploration and Development of Space. Retrieved 19 December 2019.
