NGC 6934

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NGC 6934
NGC 6934 Hubble WikiSky.jpg
NGC 6934 by Hubble Space Telescope; 3.5′ view
Observation data (J2000 epoch)
Class VIII [1]
Constellation Delphinus
Right ascension 20h 34m 11.37s [2]
Declination +07° 24′ 16.1″ [2]
Distance 52  kly (16  kpc) [3]
Apparent magnitude (V)8.83 [4]
Apparent dimensions (V)1.20′ [5]
Physical characteristics
Absolute magnitude −7.65 [6]
Mass2.95×105 [7]   M☉
Metallicity [Fe/H] = –1.47 [7] dex
Other designations Caldwell 47, NGC 6934 [8]
See also: Globular cluster, List of globular clusters

NGC 6934 (also known as Caldwell 47) is a globular cluster of stars in the northern constellation of Delphinus, about 52 kilolight-years distant from the Sun. [3] It was discovered by the German-born astronomer William Herschel on 24 September 1785. [4] The cluster is following a highly eccentric orbit (with an eccentricity of 0.81) through the Milky Way along an orbital plane that is inclined by 73° to the galactic plane. It may share a common dynamic origin with NGC 5466. [6] As of 2018, it has been poorly studied. [9]

This appears to be a Oosterhoff type I cluster with an intermediate metallicity. [10] It has an Shapley–Sawyer Concentration Class of VIII, [1] with a core radius of 15″ [3] and a half-light radius of 36″. [5] The estimated mass is 295,000 times the mass of the Sun. [7] The cluster displays photometric anomalies, with a split subgiant branch on the HR diagram. [9] Searches for variable stars have discovered 85 in the cluster field, of which 79 are of the RR Lyrae class and one is a SX Phe variable. [10] There is some evidence for a tidal tail. [11]

References

  1. 1 2 Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin, 849 (849): 11–14, Bibcode:1927BHarO.849...11S.
  2. 1 2 Goldsbury, Ryan; et al. (December 2010). "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters". The Astronomical Journal. 140 (6): 1830–1837. arXiv: 1008.2755 . Bibcode:2010AJ....140.1830G. doi:10.1088/0004-6256/140/6/1830. S2CID   119183070.
  3. 1 2 3 Hessels, J. W. T.; et al. (November 2007), "A 1.4 GHz Arecibo Survey for Pulsars in Globular Clusters", The Astrophysical Journal, 670 (1): 363–378, arXiv: 0707.1602 , Bibcode:2007ApJ...670..363H, doi:10.1086/521780, S2CID   16914232.
  4. 1 2 NGC 6934, SEDS , retrieved 2010-10-09
  5. 1 2 Forbes, Duncan A.; et al. (October 2008). "Uniting old stellar systems: from globular clusters to giant ellipticals". Monthly Notices of the Royal Astronomical Society. 389 (4): 1924–1936. arXiv: 0806.1090 . Bibcode:2008MNRAS.389.1924F. doi: 10.1111/j.1365-2966.2008.13739.x . S2CID   14108457.
  6. 1 2 Dinescu, Dana I.; et al. (October 2001). "Orbits of Globular Clusters in the Outer Galaxy: NGC 7006". The Astronomical Journal. 122 (4): 1916–1927. arXiv: astro-ph/0106259 . Bibcode:2001AJ....122.1916D. doi:10.1086/323094. S2CID   1232455.
  7. 1 2 3 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.
  8. ↑ "NGC 6934". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2020-10-08.
  9. 1 2 Marino, A. F.; et al. (June 2018). "Metallicity Variations in the Type II Globular Cluster NGC 6934". The Astrophysical Journal. 859 (2): 20. arXiv: 1804.04158 . Bibcode:2018ApJ...859...81M. doi: 10.3847/1538-4357/aabdea . S2CID   119461759. 81.
  10. 1 2 Kaluzny, J.; et al. (March 2001). "Image-Subtraction Photometry of Variable Stars in the Field of the Globular Cluster NGC 6934". The Astronomical Journal. 121 (3): 1533–1550. arXiv: astro-ph/0010303 . Bibcode:2001AJ....121.1533K. doi:10.1086/319411. S2CID   14431121.
  11. ↑ Wilhelm, R.; et al. (December 2002). "Does NGC 6934 Have a Tidal Tail?". Bulletin of the American Astronomical Society. 34: 1101. Bibcode:2002AAS...201.0702W.
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