# Messier 107

Messier 107
M107 from Hubble Space Telescope; 3.5′ view
Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
ClassX[1]
Right ascension 16h 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
Metallicity${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = –0.95[7] dex
Estimated age13.95 Gyr[7]
Other designationsC 1629-129, GCl 44, M 107, NGC 6171[4]

Messier 107 or M107, also known as NGC 6171, is a very loose globular cluster in the constellation Ophiuchus, and is the last globular cluster in the Messier Catalogue. 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 discovered by Méchain to the list of Messier objects.[8] The cluster is located 2.5° south and slightly west of the star Zeta Ophiuchi.[5]

M107 is close to the galactic plane at a distance of about 20,900 light-years from Earth[3] and 9.8 kly (3.0 kpc) from the Galactic Center.[9] The orbit of this cluster carries it through the galaxy between 9.2–12.4 kly (2.82–3.79 kpc) from the Galactic Center, with the perigalactic distance laying within the galactic bar region.[10] It is an Oosterhoff type I[11] cluster with a metallicity of –0.95[7] and is considered part of the halo population.[9] There are 22 known RR Lyrae variable stars in this cluster and a probable SX Phoenicis variable.[12]

## References

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. ^ a b 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 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. ^ a b "NGC 6171". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-16.
5. ^ a b c 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. ^ a b c 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. ^ a b 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.