Messier 107

Messier 107 or M107, also known as NGC 6171, is a very loose globular cluster in a very mildly northern part of the sky in Ophiuchus, and is the last such object in the Messier Catalogue.

Messier 107
M107 from Hubble Space Telescope; 3.5′ view
Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
ClassX[1]
Right ascension16h 32m 31.86s[2]
Declination–13° 03′ 13.6″[2]
Distance20.9 kly (6.4 kpc)[3]
Apparent magnitude (V)+8.85[4]
Apparent dimensions (V)10′[5]
Physical characteristics
Mass1.82×105[3] M☉
Radius30 ly[6]
Metallicity = –0.95[7] dex
Estimated age13.95 Gyr[7]
Other designationsC 1629-129, GCl 44, M 107, NGC 6171[4]

Observational history, namings and guide

It was discovered by Pierre Méchain in April 1782, then independently by William Herschel in 1793. Herschel described it as a "globular cluster of stars, large, very rich, very much compressed, round, well resolved, clearly consisting of stars".[5] It was not until 1947 that Helen Sawyer Hogg added it and three other objects found by Méchain to the modern Catalogue, the latter having contributed several of the suggested observation objects which Messier had verified and added.[8] The cluster is to be found 2.5° south and slightly west of the star Zeta Ophiuchi.[5]

Properties

M107 is close to the galactic plane and about 20,900 light-years from Earth[3] and 9,800 ly (3,000 pc) from the Galactic Center.[9] Its orbit is partly as far out as the galactic halo, as is between 9,200–12,400 ly (2,820–3,790 pc) from the Galactic Center, the lower figure, the "perigalactic distance" sees it enter and leave the galactic bar.[10]

It is an Oosterhoff type I[11] cluster with a metallicity of −0.95[7][lower-alpha 1] and it conforms with the bulk of the halo population.[9] There are 22 known RR Lyrae variable stars in this cluster and a probable SX Phoenicis variable.[12]

  • The globular star cluster Messier 107 image taken by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope.
  • Map showing the location of M107.

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, arXiv:1008.2755, Bibcode:2010AJ....140.1830G, doi:10.1088/0004-6256/140/6/1830.
  3. 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.
  4. "NGC 6171". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-16.
  5. Mullaney, James (2007), The Herschel Objects and How to Observe Them, Astronomers' Observing Guides, Springer Science & Business Media, p. 94, Bibcode:2007hoho.book.....M, ISBN 978-0387681252.
  6. From trigonometry: distance × sin( diameter_angle / 2 ) = 39.5 ly. radius
  7. 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.
  8. Frommert, Hartmut; Kronberg, Christine (August 30, 2007), "Messier 107", SEDS Messier pages, Students for the Exploration and Development of Space (SEDS), retrieved 2018-12-07.
  9. Zinn, R. (June 15, 1985), "The globular cluster system of the galaxy. IV - The halo and disk subsystems", Astrophysical Journal, Part 1, 293: 424–444, Bibcode:1985ApJ...293..424Z, doi:10.1086/163249.
  10. Pichardo, Bárbara; et al. (July 2004), "Models for the Gravitational Field of the Galactic Bar: An Application to Stellar Orbits in the Galactic Plane and Orbits of Some Globular Clusters", The Astrophysical Journal, 609 (1): 144–165, arXiv:astro-ph/0402340, Bibcode:2004ApJ...609..144P, doi:10.1086/421008.
  11. Olech, A.; et al. (March 2001), "The Clusters AgeS Experiment (CASE): RR Lyrae variables in the globular cluster NGC 6362", Monthly Notices of the Royal Astronomical Society, 321 (3): 421–432, arXiv:astro-ph/0005589, Bibcode:2001MNRAS.321..421O, doi:10.1046/j.1365-8711.2001.04010.x.
  12. McCombs, Thayne; et al. (January 2013), "Variable Stars in the Globular Cluster M107: The Discovery of a Probable SX Phoenicis", AAS Meeting #221, 221, American Astronomical Society, p. 250.22, Bibcode:2013AAS...22125022M, 250.22.
  1. Where minus 1 would be 10 times less iron-to-hydrogen metallicity than the Sun

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