Messier 70

Short description: Globular cluster in the constellation Sagittarius

Messier 70

Globular cluster Messier 70 by Hubble Space Telescope; 3.3′ view

Observation data (J2000 epoch)
Class| V[1]
Constellation| Sagittarius
Right ascension|  18h 43m 12.76s[2]
Declination| –32° 17′ 31.6″[3]
Distance| 29.4 kly (9.0 kpc)[4]
Apparent magnitude (V)| 7.9[5]
Apparent dimensions (V)| 8.0′[6]
Physical characteristics
Mass| 1.79×105[4] M☉
Radius| 34 ly[7]
Tidal radius| 11.2′[8]
Metallicity| [Fe/H] = –1.35[9] dex
Estimated age| 12.80 Gyr[9]
Other designations| GCl 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]

## Contents

* 1 Gallery
* 2 See also
* 3 References and footnotes
* 4 External links

## Gallery

* Image by Hubble Space Telescope

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

## See also

* List of Messier objects

## 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

* Messier 70, Galactic Globular Clusters Database page
*   * Messier 70 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

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

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Messier objects

List|

* M1
* M2
* M3
* M4
* M5
* M6
* M7
* M8
* M9
* M10
* M11
* M12
* M13
* M14
* M15
* M16
* M17
* M18
* M19
* M20
* M21
* M22
* M23
* M24
* M25
* M26
* M27
* M28
* M29
* M30
* M31
* M32
* M33
* M34
* M35
* M36
* M37
* M38
* M39
* M40
* M41
* M42
* M43
* M44
* M45
* M46
* M47
* M48
* M49
* M50
* M51
* M52
* M53
* M54
* M55
* M56
* M57
* M58
* M59
* M60
* M61
* M62
* M63
* M64
* M65
* M66
* M67
* M68
* M69
* M70
* M71
* M72
* M73
* M74
* M75
* M76
* M77
* M78
* M79
* M80
* M81
* M82
* M83
* M84
* M85
* M86
* M87
* M88
* M89
* M90
* M91
* M92
* M93
* M94
* M95
* M96
* M97
* M98
* M99
* M100
* M101
* M102
* M103
* Added
* M104
* M105
* M106
* M107
* M108
* M109
* M110

See also|

* Caldwell catalogue
* Catalogue of Nebulae and Clusters of Stars
* Herschel 400 Catalogue
* Index Catalogue
* New General Catalogue
* Revised New General Catalogue

* Book
* Category
* Commons
* Portal

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