NGC 6401
Globular cluster in the constellation Ophiuchus
| NGC 6401 | |
|---|---|
 HST image of NGC 6401 | |
| Observation data (J2000 epoch) | |
| Constellation | Ophiuchus |
| Right ascension | 17h 38m 36.93s[1] |
| Declination | −23° 54′ 31.5″[1] |
| Distance | 25.1 kly (7.70 kpc)[2] |
| Apparent magnitude (V) | 7.4[3] |
| Apparent dimensions (V) | 4.8′[3] |
| Physical characteristics | |
| Metallicity | = −1.15±0.20[4] dex |
| Estimated age | 13.2±1.2 Gyr[4] |
| Other designations | GC 4314, NGC 6301[5] |
| See also: Globular cluster, List of globular clusters | |
![{\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/4c0821bd80891e071c08e7c7ee8e022baedf522c)
NGC 6401 is a globular cluster in the equatorial constellation of Ophiuchus.[3] This star cluster was discovered by German-English astronomer William Herschel in 1784, but he mistakenly classified it as a bright nebula. Later, his son John Herschel came to the same conclusion because the technology of the day did not allow the individual stars to be visually resolved.[6] It is visible in a small telescope, with an apparent visual magnitude of 7.4 and an angular diameter of 4.8′.[3]
This cluster is located at a distance of 25.1 kly (7.70 kpc) from the Sun[2] and is orbiting in the galactic bulge, in the inner part of the Milky Way galaxy.[4] Because of its high mass, it may be gravitationally trapped inside the Milky Way's bar. From the perspective of the Earth, this cluster is situated 5.3° from the Galactic Center and is strongly reddened due to extinction from interstellar dust.[7] NGC 6401 is a very old cluster with an estimated age of 13.2±1.2 Gyr,[4] but has not undergone core collapse.[8] It has a cluster radius of 2.4′.[7]
23 class ab and 11 class c RR Lyrae variables have been identified within a cluster radius of the core. From this, it is deduced that this is an Oosterhoff type I (Oo I) cluster.[7]
References
- ^ 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 Baumgardt, H.; Hilker, M.; Sollima, A.; Bellini, A. (2019), "Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data", Monthly Notices of the Royal Astronomical Society, 482 (4): 5138–5155, arXiv:1811.01507, Bibcode:2019MNRAS.482.5138B, doi:10.1093/mnras/sty2997.
- ^ a b c d O'Meara, Stephen James (2007), Herschel 400 Observing Guide, Cambridge University Press, p. 219, ISBN 9780521858939.
- ^ a b c d Cohen, Roger E.; et al. (December 2021), "Relative Ages of Nine Inner Milky Way Globular Clusters from Proper-motion-cleaned Color-Magnitude Diagrams", The Astronomical Journal, 162 (6), id. 228, arXiv:2109.08708, Bibcode:2021AJ....162..228C, doi:10.3847/1538-3881/ac281f.
- ^ "NGC 6401". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2024-08-18.
- ^ "Enigmatic cluster targeted by Hubble", Hubble News, NASA/ESA, retrieved 2024-08-18.
- ^ a b c Tsapras, Y.; et al. (February 2017), "Variable stars in the bulge globular cluster NGC 6401", Monthly Notices of the Royal Astronomical Society, 465 (2): 2489–2504, arXiv:1610.09911, Bibcode:2017MNRAS.465.2489T, doi:10.1093/mnras/stw2773.
- ^ Cohen, Roger E.; et al. (January 2021), "Structure and Internal Kinematics of Nine Inner Milky Way Globular Clusters", The Astronomical Journal, 161 (1), id. 41, arXiv:2012.00791, Bibcode:2021AJ....161...41C, doi:10.3847/1538-3881/abd036.
External links
Media related to NGC 6401 at Wikimedia Commons- NGC 6401 SEDS.org (Revised NGC)
- NGC 6401 NASA Extragalactic Database
