NGC 6520

NGC 6520
NGC 6520 and dark nebula Barnard 86
Observation data (J2000 epoch)
Right ascension18h 03m 25.4s[1]
Declination−27° 53′ 02″[1]
Distance5,235 ly (1,605.0 pc)[1]
Apparent magnitude (V)7.6[2]
Apparent dimensions (V)6.0′[2]
Physical characteristics
Mass364±54[3] M☉
Estimated age178[1] Myr
Other designationsCr 361, Mel 187[4]
Associations
ConstellationSagittarius
See also: Open cluster, List of open clusters

NGC 6520 is an open cluster of stars in the southern constellation of Sagittarius,[5] about 4° to the east of the Galactic Center.[3] With an apparent visual magnitude of 7.6 and an angular size of 6.0′, it can be viewed with binoculars or a small telescope. Just to the west of this cluster is the dark nebula Barnard 86, dubbed the Ink Spot.[2] Both features are viewed against the dense stary background of the Large Sagittarius Star Cloud.[6] This cluster is located at a distance of approximately 5,235 ly from the Sun.[1]

This is a young open cluster of stars with age estimates yielding a values of 150 to 190 million years.[3] However, the presence of stars with a spectral class of B4 and B5 suggest a much younger age of 60 million years.[7] The estimated mass of this cluster is 364±54 M☉.[3] The cluster and the nearby dark nebula Barnard 86 have radial velocities that differ by 30 km/s, and hence may be unrelated.[7]

Two type 2 chemically peculiar stars and two Lambda Bootis candidates have been found among the members. Polarization measurements of the cluster members suggests that there are three closer dust layers partially obscuring the view from the perspective of the Earth.[8]

  • Star cluster NGC 6520 and dark nebula Barnard 86 within the Large Sagittarius Star Cloud
    Star cluster NGC 6520 and dark nebula Barnard 86 within the Large Sagittarius Star Cloud
  • Map showing the location of NGC 6520
    Map showing the location of NGC 6520
  • Kitt Peak image
    Kitt Peak image

References

  1. ^ a b c d e Tarricq, Y.; et al. (March 2021), "3D kinematics and age distribution of the open cluster population", Astronomy & Astrophysics, 647, id. A19, arXiv:2012.04017, Bibcode:2021A&A...647A..19T, doi:10.1051/0004-6361/202039388.
  2. ^ a b c Thompson, Robert Bruce; Thompson, Barbara Fritchman (2007). Illustrated Guide to Astronomical Wonders: From Novice to Master Observer. DIY Science. Maker Media, Inc. p. 410. ISBN 9781449310264.
  3. ^ a b c d Carraro, Giovanni; et al. (August 2005). "The Open Cluster NGC 6520 and the Nearby Dark Molecular Cloud Barnard 86". The Astronomical Journal. 130 (2): 635–642. arXiv:astro-ph/0504439. Bibcode:2005AJ....130..635C. doi:10.1086/431284.
  4. ^ "NGC 6520". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2024-08-22.
  5. ^ Burnham, Jr., Robert (2013). Burnham's Celestial Handbook: An observer's guide to the universe beyond the solar system. Vol. 3. Dover Publications. p. 1555. ISBN 9780486318035.
  6. ^ "Zooming into the star cluster NGC 6520 and the dark cloud Barnard 86". ESO. February 13, 2013. Retrieved 2024-08-23.
  7. ^ a b Odell, Andrew P. (January 2014). "A New Look at Open Cluster NGC 6520". The Astronomical Journal. 147 (1). id. 7. arXiv:1310.7227. Bibcode:2014AJ....147....7O. doi:10.1088/0004-6256/147/1/7.
  8. ^ Feinstein, Carlos; et al. (November 2008). "Optical polarization study in the open cluster NGC 6250". Monthly Notices of the Royal Astronomical Society. 391 (1): 447–456. Bibcode:2008MNRAS.391..447F. doi:10.1111/j.1365-2966.2008.13917.x. hdl:11336/44115.