Astronomy: General

The Columbia Encyclopedia, 6th ed. A Dictionary of Astronomy Further reading

Hercules cluster

The Columbia Encyclopedia, 6th ed. | 2011 | Copyright

Hercules cluster giant globular star cluster in the northern constellation Hercules ; cataloged as M13 or NGC 6205. The cluster is just visible to the naked eye and is the best example of a globular cluster visible in the Northern Hemisphere. Its angular diameter is about 2/3 that of the full moon, and its linear diameter is 100 light-years . The entire cluster contains perhaps 100,000 or more stars. In its central portion, the stars are so close together that they cannot be resolved, despite the cluster's relatively near distance of 35,000 light-years; the separation between stars is estimated to be only a few astronomical units as compared to the normal interstellar separation of a few light-years.

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Hercules Cluster

A Dictionary of Astronomy | 1997 | Copyright

Hercules Cluster A loose, irregular cluster of galaxies some 500 million l.y. away in the constellation Hercules; also known as Abell 2151. The cluster is 1°.7 wide as seen from Earth, has a true diameter of 6 million l.y., is flattened in shape, and is notable for the high proportion of spirals among its bright members. There are about 75 bright galaxies, and many fainter members.

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"Hercules Cluster." A Dictionary of Astronomy. 1997. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>.

"Hercules Cluster." A Dictionary of Astronomy. 1997. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O80-HerculesCluster.html

"Hercules Cluster." A Dictionary of Astronomy. 1997. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-HerculesCluster.html

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Free newspaper and magazine articles

	NIGHT SKY: MIGHTY HERCULES IN THE SUMMER NIGHT SKY.(Outdoors) Newspaper article from: The Santa Fe New Mexican (Santa Fe, NM); 6/5/2008
	Astro Camp and beyond ... (Wow! Fantastic Journeys). Magazine article from: The Evening Standard (London, England); 4/1/2003
	PUBLIC WORKS: STARGAZE AT STATE PARKS.(Neighbors) Newspaper article from: The Santa Fe New Mexican (Santa Fe, NM); 6/11/2006