Astronomy:NGC 6934

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Short description: Globular cluster in the constellation Delphinus
NGC 6934
NGC 6934 Hubble WikiSky.jpg
NGC 6934 by Hubble Space Telescope; 3.5′ view
Observation data (J2000 epoch)
ClassVIII[1]
ConstellationDelphinus
Right ascension 20h 34m 11.37s[2]
Declination+07° 24′ 16.1″[2]
Distance52 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[math]\displaystyle{ \begin{smallmatrix}\left[\ce{Fe}/\ce{H}\right]\end{smallmatrix} }[/math] = –1.47[7] dex
Other designationsCaldwell 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. ↑ 1.0 1.1 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. ↑ 2.0 2.1 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. doi:10.1088/0004-6256/140/6/1830. Bibcode: 2010AJ....140.1830G. 
  3. ↑ 3.0 3.1 3.2 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, doi:10.1086/521780, Bibcode: 2007ApJ...670..363H. 
  4. ↑ 4.0 4.1 NGC 6934, SEDS, http://spider.seds.org/spider/MWGC/n6934.html, retrieved 2010-10-09 
  5. ↑ 5.0 5.1 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. doi:10.1111/j.1365-2966.2008.13739.x. Bibcode: 2008MNRAS.389.1924F. 
  6. ↑ 6.0 6.1 Dinescu, Dana I. et al. (October 2001). "Orbits of Globular Clusters in the Outer Galaxy: NGC 7006". The Astronomical Journal 122 (4): 1916–1927. doi:10.1086/323094. Bibcode: 2001AJ....122.1916D. 
  7. ↑ 7.0 7.1 7.2 Boyles, J. et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal 742 (1): 51, doi:10.1088/0004-637X/742/1/51, Bibcode: 2011ApJ...742...51B. 
  8. ↑ "NGC 6934". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+6934. 
  9. ↑ 9.0 9.1 Marino, A. F. et al. (June 2018). "Metallicity Variations in the Type II Globular Cluster NGC 6934". The Astrophysical Journal 859 (2): 20. doi:10.3847/1538-4357/aabdea. 81. Bibcode: 2018ApJ...859...81M. 
  10. ↑ 10.0 10.1 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. doi:10.1086/319411. Bibcode: 2001AJ....121.1533K. 
  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. 

External links

Coordinates: Sky map 20h 34m 11.5s, +07° 24′ 14.9″



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