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Messier 13

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**Messier 13**
Observation data: J2000 epoch

Class:	V
Constellation:	Hercules
Right ascension:	16^h 41^m 41.44^s^[1]
Declination:	+36° 27′ 36.9″^[1]
Distance:	25.1 kly ()
Apparent magnitude (V):	+5.8^[1]
Apparent dimensions (V):	23′
Physical characteristics
Mass:	( M_☉)
Radius:	84 ly^[2]
V_HB:
Estimated age:	1.4×10¹⁰ yr
Notable features:	one of the best well-known clusters of the northern hemisphere
Other designations:	NGC 6205^[1]
See also: Globular cluster, List of globular clusters

The Great Globular Cluster in Hercules (also known as the Hercules Globular Cluster, Messier Object 13, Messier 13, M13, or NGC 6205) is a globular cluster in the Hercules constellation at right ascension 16^h 41.7^m and declination +36° 28'. It was discovered by Edmond Halley in 1714, and catalogued by Charles Messier on June 1, 1764. With an apparent magnitude of 5.8, it is barely visible with the naked eye on a very clear night. Its real diameter is about 145 light-years, and is composed of several hundred thousand stars, the brightest of which is the variable star V11 with an apparent magnitude of 11.95. M13 is 25,100 light-years away from Earth. Its diameter is about 23 arc minutes and is readily viewable in small telescopes. Nearby is NGC 6207, a 12th magnitude edge on galaxy that lies 28 arc minutes directly north east. The J2000 coordinates are RA: 16h 41m 41.5s and Dec: +36° 27' 37". IC 4617 is a small galaxy that lies half-way between NGC 6207 and M13, North-northeast of the large globular's center. The Arecibo message of 1974 was transmitted toward this globular cluster. The reason was that with a higher star density the chances of a life harboring planet, with intelligent life forms, were higher.

1 Literary references
2 See also
3 External links
4 References

Literary references

The science fiction novellas "Sucker Bait" by Isaac Asimov and "Question and Answer" by Poul Anderson take place on Troas, a world within M13.
In the science fiction series Perry Rhodan, M13 is the location of Arkon, the home world of the race of Arkonides.
In author Dan Simmon's Hyperion Cantos the Hercules cluster is where Earth was secretly moved to after it was supposedly destroyed.
In The Sirens of Titan, Kurt Vonnegut writes "Every passing hour brings the Solar System forty-three thousand miles closer to Globular Cluster M13 in Hercules -- and still there are some misfits who insist that there is no such thing as progress."

External links

References

^ ^a ^b ^c ^d SIMBAD Astronomical Database. Results for NGC 6205. Retrieved on 2006-11-15.
^ distance × sin( diameter_angle / 2 ) = 84 ly. radius