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Messier 13

Messier 13
The heart of Hercules Globular Cluster;
Credit: ESA/Hubble and NASA
Observation data (J2000 epoch)
Class V[1]
Constellation Hercules
Right ascension 16h 41m 41.24s[2]
Declination +36° 27′ 35.5″[2]
Distance 22.2 kly (6.8 kpc)[3]
Apparent magnitude (V) +5.8[4]
Apparent dimensions (V) 20 arcmins
Physical characteristics
Mass 6×105[5] M
Radius 84 ly[6]
Metallicity –1.7[7] dex
Estimated age 11.65 Gyr[7]
Notable features one of the best-known clusters of the northern hemisphere
Other designations NGC 6205[4]

Messier 13 (M13), also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster, is a globular cluster of about 300,000 stars in the constellation of Hercules.


  • Discovery and visibility 1
  • Characteristics 2
  • Arecibo message 3
  • Literary references 4
  • See also 5
  • References 6
  • External links 7

Discovery and visibility

M13 was discovered by Edmond Halley in 1714, and catalogued by Charles Messier on June 1, 1764.

It is located at right ascension 16h 41.7m and declination +36° 28'. With an apparent magnitude of 5.8, it is barely visible with the naked eye on a very clear night. Its diameter is about 23 arc minutes and it is readily viewable in small telescopes. Nearby is NGC 6207, a 12th magnitude edge-on galaxy that lies 28 arc minutes directly north east. A small galaxy, IC 4617, lies halfway between NGC 6207 and M13, north-northeast of the large globular cluster's center.

Wide field image of Messier 13.


M13 is about 145 light-years in diameter, and it is composed of several hundred thousand stars, the brightest of which is a red giant, the variable star V11, with an apparent visual magnitude of 11.95. M13 is 25,100 light-years away from Earth.

Arecibo message

The Arecibo message of 1974, which contained encoded information about the human race, DNA, atomic numbers, Earth's position and other information, was beamed from the Arecibo Observatory radio telescope towards M13 as an experiment in contacting potential extraterrestrial civilizations in the cluster. While the cluster will move through space during the transit time, the proper motion is small enough that the cluster will only move 24 light years, only a fraction of the diameter of the cluster. Thus, the message will still arrive near the center of the cluster.[8]

Literary references

M13 is in "armpit" of Hercules constellation

See also


  1. ^ Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin 849 (849): 11–14,  
  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,  
  3. ^ Paust, Nathaniel E. Q.; et al. (February 2010), "The ACS Survey of Galactic Globular Clusters. VIII. Effects of Environment on Globular Cluster Global Mass Functions", The Astronomical Journal 139 (2): 476–491,  
  4. ^ a b "SIMBAD Astronomical Object Database". Results for NGC 6205. Retrieved 2006-11-15. 
  5. ^ Leonard, Peter J. T.; Richer, Harvey B.; Fahlman, Gregory G. (1992), "The mass and stellar content of the globular cluster M13",  
  6. ^ distance × sin( diameter_angle / 2 ) = 84 ly radius
  7. ^ a b Forbes, Duncan A.; Bridges, Terry (May 2010), "Accreted versus in situ Milky Way globular clusters",  
  8. ^ "Science 2.0". In regard to the email from. Retrieved 2015-04-15. 

External links

  • Messier 13, SEDS Messier pages
  • Red Giant variable stars
  • Messier 13, Galactic Globular Clusters Database page
  • Messier 13, High-resolution LRGB image based on 2 hrs total exposure
  • Messier 13, Amateur astrophotographer (hgg) photo using the 9.25" Celestron Telescope (85min exposure)
  • M13 Hercules Globular photo detail Dark Atmospheres
  • Messier 13, Image by Waid Observatory
  • – M13, the Hercules Globular Cluster
  • Photometric study of the V2 cepheid in M13
  • Period, Amplitude and Light Curve of V38 in M13
  • Great Globular Cluster in Hercules (Messier 13/NGC 6205)
  • Rothery, David; Bauer, Amanda; Dhillon, Vik; Lawrence, Pete;  
  • Messier 13 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

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