Astronomy:Messier 70

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Short description: Globular cluster in the constellation Sagittarius
Messier 70
Messier70-HST-Potw1215a.jpg
Globular cluster Messier 70 by Hubble Space Telescope; 3.3′ view
Observation data (J2000 epoch)
ClassV[1]
ConstellationSagittarius
Right ascension 18h 43m 12.76s[2]
Declination–32° 17′ 31.6″[3]
Distance29.4 kly (9.0 kpc)[4]
Apparent magnitude (V)7.9[5]
Apparent dimensions (V)8.0′[6]
Physical characteristics
Mass1.79×105[4] M☉
Radius34 ly[7]
Tidal radius11.2′[8]
Metallicity[math]\displaystyle{ \begin{smallmatrix}\left[\ce{Fe}/\ce{H}\right]\end{smallmatrix} }[/math] = –1.35[9] dex
Estimated age12.80 Gyr[9]
Other designationsGCl 101, M70, NGC 6681[3]
See also: Globular cluster, List of globular clusters

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]

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]

Gallery

  • Image by Hubble Space Telescope

  • Map showing M70, against a conventional (southern) horizon

See also

References and footnotes

  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. ↑ 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 "NGC 6681". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+6681. 
  4. ↑ 4.0 4.1 4.2 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. 
  5. ↑ "Messier 70". https://messier.seds.org/m/m070.html. 
  6. ↑ 6.0 6.1 Adam, Len (2018), Imaging the Messier Objects Remotely from Your Laptop, The Patrick Moore Practical Astronomy Series, Springer, p. 304, ISBN 978-3319653853, Bibcode: 2018imor.book.....A, https://books.google.com/books?id=7nNUDwAAQBAJ&pg=PA304 
  7. ↑ distance × sin( diameter_angle / 2 ) = 34 ly. radius
  8. ↑ 8.0 8.1 Liller, M. H. (October 1983), "The variable stars in the field of the globular cluster NGC 6681", Astronomical Journal 88: 1463–1469, doi:10.1086/113435, Bibcode: 1983AJ.....88.1463L. 
  9. ↑ 9.0 9.1 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, doi:10.1111/j.1365-2966.2010.16373.x, Bibcode: 2010MNRAS.404.1203F. 
  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, https://books.google.com/books?id=dfO7BAAAQBAJ&pg=PA483 
  11. ↑ 11.0 11.1 11.2 Watson, Alan M. et al. (November 1994), "Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2", Astrophysical Journal, Part 2 435 (1): L55–L58, doi:10.1086/187593, Bibcode: 1994ApJ...435L..55W, https://authors.library.caltech.edu/53635/1/1994ApJ___435L__55W.pdf. 
  12. ↑ Frommert, Hartmut; Kronberg, Christine (30 August 2007), "Globular Cluster M70", SEDS Messier pages (Students for the Exploration and Development of Space (SEDS)), http://messier.seds.org/m/m070.html, retrieved 2018-12-04. 
  13. ↑ Djorgovski, S. (January 1993), "Physical Parameters of Galactic Globular Clusters", in Djorgovski, S. G.; Meylan, G., 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, 50, San Francisco, California: Astronomical Society of the Pacific, pp. 373, ISBN 978-0937707692, Bibcode: 1993ASPC...50..373D. 
  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, doi:10.1111/j.1365-2966.2008.13739.x, Bibcode: 2008MNRAS.389.1924F. 
  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, doi:10.1086/115160, Bibcode: 1989AJ.....98..596P. 
  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, doi:10.3847/1538-4357/aa7b72, 23, Bibcode: 2017ApJ...846...23O. 
  17. ↑ Clement, Christine M. et al. (November 2001), "Variable Stars in Galactic Globular Clusters", The Astronomical Journal 122 (5): 2587–2599, doi:10.1086/323719, Bibcode: 2001AJ....122.2587C. 
  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

External links

Coordinates: Sky map 18h 43m 12.64s, −32° 17′ 30.8″



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