# Messier 9

Messier 9
Messier 9 by HST
Credit: NASA/ESA
Observation data (J2000 epoch)
Class VIII[1]
Constellation Ophiuchus
Right ascension 17h 19m 11.78s[2]
Declination –18° 30′ 58.5″[2]
Distance 25.8 kly (7.9 kpc)[3]
Apparent magnitude (V) +8.42[2]
Apparent dimensions (V) 12′.0
Physical characteristics
Mass 4.22×105[3] M
Metallicity $\begin{smallmatrix}\left[{Fe}/{H}\right]\end{smallmatrix}$ = –1.77[3] dex
Estimated age 12.0 Gyr[4]
Other designations NGC 6333[2]

Messier 9 or M9 (also designated NGC 6333) is a globular cluster in the constellation of Ophiuchus. It was discovered by Charles Messier in 1764.

M9 is one of the nearer globular clusters to the center of the Milky Way Galaxy with a distance of around 5,500 light-years. Its distance from Earth is 25,800 light-years.

The total luminosity of this cluster is around 120,000 times that of the Sun, the absolute magnitude being -8.04. The brightest individual stars in M9 are of apparent magnitude 13.5, making them visible in moderately sized telescopes. There have been 13 variable stars found in M9.

Nearby, at about 80' to the northeast of M9 is the dimmer globular cluster NGC 6356, while at about 80' to the southeast is the globular NGC 6342.

## 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. ^ a b c d "SIMBAD Astronomical Database". Results for NGC 6333. Retrieved 2006-11-15.
3. ^ a b c d 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. ^ Koleva, M.; et al. (April 2008), "Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting", Monthly Notices of the Royal Astronomical Society 385 (4): 1998–2010, arXiv:0801.0871, Bibcode:2008MNRAS.385.1998K, doi:10.1111/j.1365-2966.2008.12908.x