# Messier 10

(Redirected from Globular Cluster M10)
Messier 10
The core region of Messier 10 by Hubble Space Telescope; 3.5′ view
Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
Class VII[1]
Constellation Ophiuchus
Right ascension 16h 57m 8.92s[2]
Declination −04° 05′ 58.07″[2]
Distance 14.3 kly (4.4 kpc)[3]
Apparent magnitude (V) 6.4[4]
Apparent dimensions (V) 20′.0
Physical characteristics
Mass 2.25 × 105[5] M
Metallicity ${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = –1.25[7] dex
Estimated age 11.39 Gyr[7]
Other designations GCl-49, NGC 6254[4]
See also: Globular cluster, List of globular clusters

Messier 10 or M10 (also designated NGC 6254) is a globular cluster of stars in the equatorial constellation of Ophiuchus. The object was discovered by the French astronomer Charles Messier on May 29, 1764, who cataloged it as number 10 in his catalogue and described it as a "nebula without stars". In 1774, German astronomer Johann Elert Bode likewise called it a "nebulous patch without stars; very pale". Using larger instrumentation, German-born astronomer William Herschel was able to resolve the cluster into its individual members. He described it as a "beautiful cluster of extremely compressed stars". William Parsons, 3rd Earl of Rosse thought he could distinguish a dark lane through part of the cluster. The first to estimate the distance to the cluster was Harlow Shapley, although his derivation of 33,000 light years was much further than the modern value.[8]

Messier 10 with amateur telescope
Map showing the location of M10

The tidal radius of M10 is 19.3 arcminutes, which is about two-thirds of the apparent diameter of the Moon. Viewed through medium-sized telescopes it appears about half that size (8–9 arcminutes), as its bright core is only 35 light-years across. It has a core radius of 48 arcseconds and a half-mass radius of 147 arcseconds (2.5 arcminutes).[2] M10 has a spatial diameter of 83 light-years and is estimated to be 14,300 light-years away from Earth.[3]

In terms of the abundance of elements other than hydrogen and helium, what astronomers term the metallicity, Messier 10 is "moderately metal–poor". The abundance of iron, measured as [Fe/H] equals –1.45 ± 0.04 dex, is only 3.5% of the abundance found at the surface of the Sun.[9] The cluster shows evidence of being enriched by the elements generated through the s-process in massive stars and Type II supernovae. It shows little evidence of enrichment by Type 1a supernovae.[10]

Because binary stars are, on average, more massive than normal stars, the binaries tend to migrate toward the center of the cluster. The fraction of binary stars in the core region is about 14%. This proportion decreases with increasing radius to about 1.5% in the outlying regions of the cluster.[2] Correspondingly, the core region contains a concentration of interaction-formed blue straggler stars, most of which formed 2–5 billion years ago.[11] The density of stars in the core region is about 3.8 solar masses per cubic parsec.[2] Four variable stars have been discovered in this cluster.

The cluster is currently located about 5 kiloparsecs (16 kly) from the Galactic Center.[10] It completes an orbit around the Milky Way galaxy about every 140 million years, during which it crosses the plane of the galactic disk every 53 million years. Its rosette orbit has an eccentricity of 0.21.[5]

## References

1. ^ Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin (849): 11–14, Bibcode:1927BHarO.849...11S.
2. Dalessandro, E.; et al. (December 2011), "The Binary Fraction in the Globular Cluster M10 (NGC 6254): Comparing Core and Outer Regions", The Astrophysical Journal 743 (1): 11, arXiv:1108.5675, Bibcode:2011ApJ...743...11D, doi:10.1088/0004-637X/743/1/11.
3. ^ a b Bica, E.; et al. (April 2006), "Globular cluster system and Milky Way properties revisited", Astronomy and Astrophysics 450 (1): 105–115, arXiv:astro-ph/0511788, Bibcode:2006A&A...450..105B, doi:10.1051/0004-6361:20054351.
4. ^ a b "M 10 -- Globular Cluster", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2010-03-19.
5. ^ a b Gnedin, Oleg Y.; Lee, Hyung Mok; Ostriker, Jeremiah P. (1999), "Effects of Tidal Shocks on the Evolution of Globular Clusters", Astrophysical Journal 522 (2): 935–949, arXiv:astro-ph/9806245, Bibcode:1999ApJ...522..935G, doi:10.1086/307659.
6. ^ distance × sin( diameter_angle / 2 ) = 41.6 ly. radius
7. ^ 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.
8. ^ Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the Solar System, Dover Books on Astronomy 2 (2nd ed.), Courier Dover Publications, p. 1261, ISBN 0486235688.
9. ^ Since 10−1.45 = 0.035.
10. ^ a b Haynes, Sharina; Burks, Geoffrey; Johnson, Christian I.; Pilachowski, Catherine A. (October 2008), "Chemical Analysis of Five Red Giants in the Globular Cluster M10 (NGC 6254)", The Publications of the Astronomical Society of the Pacific 120 (872): 1097–1102, arXiv:0808.2480, Bibcode:2008PASP..120.1097H, doi:10.1086/592717.
11. ^ Ferraro, Francesco R.; et al. (May 2003), "Blue Straggler Stars: A Direct Comparison of Star Counts and Population Ratios in Six Galactic Globular Clusters", The Astrophysical Journal 588 (1): 464–477, arXiv:astro-ph/0301261, Bibcode:2003ApJ...588..464F, doi:10.1086/374042.