Messier_70

Messier 70

Messier 70

Globular cluster in the constellation Sagittarius

Messier 70 or M70, also known as NGC 6681, is a globular cluster of stars to be found in the south of Sagittarius.[lower-alpha 1] It was discovered by Charles Messier in 1780.[lower-alpha 2][6] The famous comet Hale–Bopp was discovered near this cluster in 1995.[10][lower-alpha 3]

Quick Facts Observation data (J2000 epoch), Class ...

It is about 29,400[4] light years away from Earth and around 6,500 light-years[11] from the Galactic Center. It is roughly the same size and luminosity as its neighbour in space, M69.[12] M70 has a very small core radius of 0.22 ly (0.068 pc)[13] and a half-light radius of 182.0 ly (55.80 pc).[14] This cluster has undergone core collapse, leaving it centrally concentrated[15] with the luminosity distribution following a power law.[11]

There are two distinct stellar populations in the cluster, with each displaying unique abundance abundances. These likely represent different generations of stars.[16] Five known variable stars lie within the broadest radius, the tidal radius, of it, all of which are RR Lyrae variables.[8][17] The cluster may have two blue stragglers near the core.[11]

  • Image by Hubble Space Telescope
  • Map showing M70, against a conventional (southern) horizon

See also

References and footnotes

  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]
    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. [3]
    "NGC 6681". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 17 November 2006.
  4. [4]
    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.
  5. [5]
    "Messier 70". SEDS Messier Catalog. Retrieved 30 April 2022.
  6. [6]
    Adam, Len (2018), Imaging the Messier Objects Remotely from Your Laptop, The Patrick Moore Practical Astronomy Series, Springer, p. 304, Bibcode:2018imor.book.....A, ISBN 978-3319653853
  7. [7]
    distance × sin( diameter_angle / 2 ) = 34 ly. radius
  8. [8]
    Liller, M. H. (October 1983), "The variable stars in the field of the globular cluster NGC 6681", Astronomical Journal, 88: 1463–1469, Bibcode:1983AJ.....88.1463L, doi:10.1086/113435.
  9. [9]
    Forbes, Duncan A.; Bridges, Terry (May 2010), "Accreted versus in situ Milky Way globular clusters", Monthly Notices of the Royal Astronomical Society, 404 (3): 1203–1214, arXiv:1001.4289, Bibcode:2010MNRAS.404.1203F, doi:10.1111/j.1365-2966.2010.16373.x, S2CID 51825384.
  10. [10]
    Mobberley, Martin (2013), It Came From Outer Space Wearing an RAF Blazer!: A Fan's Biography of Sir Patrick Moore, Springer Science & Business Media, p. 483, ISBN 978-3319006093
  11. [11]
    Watson, Alan M.; et al. (November 1994), "Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2" (PDF), Astrophysical Journal, Part 2, 435 (1): L55–L58, Bibcode:1994ApJ...435L..55W, doi:10.1086/187593.{{citation}}: CS1 maint: multiple names: authors list (link)
  12. [12]
    Frommert, Hartmut; Kronberg, Christine (30 August 2007), "Globular Cluster M70", SEDS Messier pages, Students for the Exploration and Development of Space (SEDS), retrieved 4 December 2018.
  13. [13]
    Djorgovski, S. (January 1993), "Physical Parameters of Galactic Globular Clusters", in Djorgovski, S. G.; Meylan, G. (eds.), Structure and Dynamics of Globular Clusters. Proceedings of a Workshop held in Berkeley, California, July 15–17, 1992, to Honor the 65th Birthday of Ivan King, vol. 50, San Francisco, California: Astronomical Society of the Pacific, p. 373, Bibcode:1993ASPC...50..373D, ISBN 978-0937707692.
  14. [14]
    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.
  15. [15]
    Pryor, Carlton; et al. (August 1989), "Mass-to-light ratios for globular clusters. I - The centrally concentrated clusters NGC 6624, M28 (NGC 6626), and M70 (NGC 6681)", Astronomical Journal, 98: 596–610, Bibcode:1989AJ.....98..596P, doi:10.1086/115160.
  16. [16]
    O'Malley, Erin M.; et al. (September 2017), "High-resolution Spectroscopic Abundances of Red Giant Branch Stars in NGC 6681", The Astrophysical Journal, 846 (1): 15, arXiv:1706.06962, Bibcode:2017ApJ...846...23O, doi:10.3847/1538-4357/aa7b72, S2CID 118972140, 23.
  17. [17]
    Clement, Christine M.; et al. (November 2001), "Variable Stars in Galactic Globular Clusters", The Astronomical Journal, 122 (5): 2587–2599, arXiv:astro-ph/0108024, Bibcode:2001AJ....122.2587C, doi:10.1086/323719, S2CID 38359010.
  1. On the southernmost line of the main (teapot) asterism; its declination means it will not rise (above the horizon) above the 58th parallel north and will need the observer to be as much as a further fifteen degrees of latitude south for detailed, little distorted observation
  2. on 31 August
  3. on 23 July
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