Messier 70

Messier 70 or M70, also known as NGC 6681, is a globular cluster of stars in the southern constellation of Sagittarius. It was discovered by Charles Messier on 31 August 1780.[5] The famous comet Hale–Bopp was discovered near this cluster 23 July 1995.[9]

M70 is at a distance of about 29,400[4] light years away from Earth and around 6,500 light-years[10] from the Galactic Center. It is roughly the same size and luminosity as its neighbour in space, M69.[11] M70 has a very small core radius of 0.22 ly (0.068 pc)[12] and a half-light radius of 182.0 ly (55.80 pc).[13] This cluster has undergone core collapse, leaving it centrally concentrated[14] with the luminosity distribution following a power law.[10]

There are two distinct stellar populations in the cluster, with each displaying unique abundance abundances. These likely represent different generations of stars.[15] Five known variable stars lie within the tidal radius of this cluster, all of which are RR Lyrae variables.[7][16] The cluster may have two blue stragglers near the core.[10]

Messier 70
Messier 70 Hubble WikiSky
M70 from Hubble Space Telescope; 3.32′ view
Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
Right ascension 18h 43m 12.76s[2]
Declination–32° 17′ 31.6″[3]
Distance29.4 kly (9.0 kpc)[4]
Apparent magnitude (V)+9.06[3]
Apparent dimensions (V)8.0[5]
Physical characteristics
Mass1.79×105[4] M
Radius34 ly[6]
Tidal radius11.2′[7]
Metallicity = –1.35[8] dex
Estimated age12.80 Gyr[8]
Other designationsGCl 101, M70, NGC 6681[3]



Picture obtained with the Wide Field Camera of Hubble's Advanced Camera for Surveys. The field of view is around 3.3 by 3.3 arcminutes.[17]


Map showing location of M70 (Roberto Mura)


  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, arXiv:1008.2755, Bibcode:2010AJ....140.1830G, doi:10.1088/0004-6256/140/6/1830.
  3. ^ a b c "NGC 6681". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-17.
  4. ^ a b c 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.
  5. ^ a b Adam, Len (2018), Imaging the Messier Objects Remotely from Your Laptop, The Patrick Moore Practical Astronomy Series, Springer, p. 304,, ISBN 978-3319653853
  6. ^ distance × sin( diameter_angle / 2 ) = 34 ly. radius
  7. ^ a b 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.
  8. ^ a b 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.
  9. ^ 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
  10. ^ a b c 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, Bibcode:1994ApJ...435L..55W, doi:10.1086/187593.
  11. ^ Frommert, Hartmut; Kronberg, Christine (30 August 2007), "Globular Cluster M70", SEDS Messier pages, Students for the Exploration and Development of Space (SEDS), retrieved 2018-12-04.
  12. ^ 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, p. 373, Bibcode:1993ASPC...50..373D, ISBN 978-0937707692.
  13. ^ 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.
  14. ^ 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.
  15. ^ 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, 23.
  16. ^ 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.
  17. ^ "Tight and Bright". ESA/Hubble Picture of the Week. Retrieved 13 April 2012.

External links

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

List of NGC objects (6001–7000)

This is a list of NGC objects 6001–7000 from the New General Catalogue (NGC). The astronomical catalogue is composed mainly of star clusters, nebulae, and galaxies. Other objects in the catalogue can be found in the other subpages of the list of NGC objects.

The constellation information in these tables is taken from The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer, which was accessed using the "VizieR Service". Galaxy types are identified using the NASA/IPAC Extragalactic Database. The other data of these tables are from the SIMBAD Astronomical Database unless otherwise stated.

Messier object

The Messier objects are a set of 110 astronomical objects cataloged by the French astronomer Charles Messier in his Catalogue des Nébuleuses et des Amas d'Étoiles ("Catalogue of Nebulae and Star Clusters").

Because Messier was interested in finding only comets, he created a list of non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as the Messier catalogue. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier number.

The catalogue includes some astronomical objects that can be observed from Earth's Northern Hemisphere such as deep-sky objects, a characteristic which makes the Messier objects extremely popular targets for amateur astronomers.A preliminary version first appeared in the Memoirs of the French Academy of Sciences in 1771,

and the last item was added in 1966 by Kenneth Glyn Jones, based on Messier's observations.

The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, with only 17 of the 45 objects being Messier's.

By 1780 the catalogue had increased to 80 objects. The final version of the catalogue containing 103 objects was published in 1781 in the Connaissance des Temps for the year 1784.

However, due to what was thought for a long time to be the incorrect addition of Messier 102, the total number remained 102. Other astronomers, using side notes in Messier's texts, eventually filled out the list up to 110 objects.The catalogue consists of a diverse range of astronomical objects, ranging from star clusters and nebulae to galaxies. For example, Messier 1 is a supernova remnant, known as the Crab Nebula, and the great spiral Andromeda Galaxy is M31. Many further inclusions followed in the next century when the first addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding Messier's side note in his 1781 edition exemplar of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967.

Thomas Bopp

Thomas Joel Bopp (October 15, 1949 – January 5, 2018) was an American amateur astronomer best known as the co-discoverer of comet Hale–Bopp (with Alan Hale) in 1995. At the time of the comet discovery he was a manager at a construction materials factory and an amateur astronomer. On the night of July 22, Bopp was observing the sky with friends in the Arizona desert when he made the discovery. It was the first comet he had observed and he was using a borrowed, home-built telescope. Hale and Bopp both discovered the comet by chance at approximately the same time.

See also

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