Messier Index/M13

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Messier 13 by Hubble Space Telescope; 3.3′ view
Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
Right ascension16h 41m 41.44s[1]
Declination+36° 27′ 36.9″[1]
Distance25.1 kly ()
Apparent magnitude (V)+5.8[1]
Apparent dimensions (V)23′
Physical characteristics
Mass1036 kg (6×105 [2] M)
Radius84 ly[3]
Estimated age1.4×1010 yr
Notable featuresone of the best
well-known clusters
of the northern
Other designationsNGC 6205[1]

Messier 13 or M13 (also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster) is a w:globular cluster in the w:constellation of Hercules.

Discovery and visibility

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

It is located at w:right ascension 16h 41.7m and w:declination +36° 28'. With an w:apparent magnitude of 5.8, it is barely visible with the w:naked eye on a very clear night. Its diameter is about 23 arc minutes and it is readily viewable in small telescopes. Nearby is w: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's center.


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

Arecibo message

The w:Arecibo message of 1974, designed to communicate the existence of human life to hypothetical extraterrestrials, was transmitted toward M13. The reason was that with a higher star density, the chances of a life harboring planet with intelligent life forms, were higher.

Literary references

M13 is in "armpit" of Hercules constellation


  1. a b c d "SIMBAD Astronomical Database". Results for NGC 6205. Retrieved 2006-11-15.
  2. Leonard, Peter J. T.; Richer, Harvey B.; Fahlman, Gregory G. "The mass and stellar content of the globular cluster M13".{{cite web}}: CS1 maint: multiple names: authors list (link)
  3. distance × sin( diameter_angle / 2 ) = 84 ly. radius