NGC 6539
| NGC 6539 | |
|---|---|
 Globular cluster NGC 6539 | |
| Observation data (J2000 epoch) | |
| Class | X:[1] |
| Constellation | Serpens |
| Right ascension | 18h 04m 49.74s[2] |
| Declination | –07° 35′ 09.1″[2] |
| Distance | 26.63 kly (8.165 kpc)[3] |
| Apparent magnitude (V) | 9.6[4] |
| Apparent dimensions (V) | 6.9′[4] |
| Physical characteristics | |
| Absolute magnitude | −8.21[2] |
| Mass | 5.36×105[5] M☉ |
| Metallicity | = −0.66[2] dex |
| Other designations | GCL 85 |
![{\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/4c0821bd80891e071c08e7c7ee8e022baedf522c)
NGC 6539, or GCL 85, is a globular cluster of stars in the constellation Serpens. It was discovered by Danish astronomer Theodor Brorsen in 1856.[6][7] This cluster is visible with a small amateur telescope, having an apparent visual magnitude of 9.6 and an angular size of 6.9″.[4] It is located at a distance of 26.63 kly (8.165 kpc) from the Sun,[3] and 10 kly (3.1 kpc) from the Galactic Center.[2]
This cluster is located in the outer parts of the Galactic bulge. There is a large dark cloud complex located in the fore of this cluster, causing reddening from extinction.[8] NGC 6539 has a core radius of 0.54′, a half-mass radius of 1.67′, and a tidal radius of 21.5′. Compared to other globular clusters, NGC 6539 is considered metal rich, indicating that it has a relatively higher abundance of elements more massive than helium. Thirteen variable stars have been detected within 7′ of the core, of which a dozen are long period variables.[9] A millisecond pulsar was discovered in 1990.[10]
References
[edit]- ^ Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin, 849 (849): 11–14, Bibcode:1927BHarO.849...11S.
- ^ a b c d e 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.; Vasiliev, E. (2021), "Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST, and literature data", Monthly Notices of the Royal Astronomical Society, 505 (4): 5957–5977, arXiv:2105.09526, Bibcode:2021MNRAS.505.5957B, doi:10.1093/mnras/stab1474.
- ^ a b c Gilmour, Jess K. (2012), The Practical Astronomer's Deep-sky Companion, Springer London, p. 120, ISBN 9781447100713.
- ^ Boyles, J.; et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal, 742 (1): 51, arXiv:1108.4402, Bibcode:2011ApJ...742...51B, doi:10.1088/0004-637X/742/1/51, S2CID 118649860.
- ^ Normandin, George (October 20, 2000), "Globular Star Cluster NGC 6539", Kopernik Space Images, archived from the original on 2006-09-28, retrieved 2006-09-28.
- ^ Patterson, Bill (June 20, 2008), "Global CLusters 2007 Gallery", LAAstro, retrieved 2012-04-09.
- ^ Origlia, L.; et al. (November 2005), "Near-infrared photometry and spectroscopy of NGC 6539 and UKS 1: two intermediate metallicity bulge globular clusters", Monthly Notices of the Royal Astronomical Society, 363 (3): 897–904, arXiv:astro-ph/0508169, Bibcode:2005MNRAS.363..897O, doi:10.1111/j.1365-2966.2005.09490.x.
- ^ Baker, JoDee M.; et al. (January 2007), "Variable Stars in Metal-Rich Globular Clusters. III. NGC 6539", The Astronomical Journal, 133 (1): 139–146, Bibcode:2007AJ....133..139B, doi:10.1086/509638.
- ^ D'Amico, N.; et al. (May 1990), Green, D. W. E. (ed.), "Millisecond Pulsar in NGC 6539", IAU Circular, 5013: 1, Bibcode:1990IAUC.5013....1D.
External links
[edit]
Media related to NGC 6539 at Wikimedia Commons
