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The Great Cluster In Hercules (M13)
Becky Stegink

Previous imageUp to Astr110 IndexNext imageHercules Globular Star Cluster M13

The Great Cluster in Hercules was discovered in 1714 by Edmond Halley.  However, the cluster was not cataloged until June 1, 1764.  The cluster is located 25,100 lightyears away from earth in the constellation of “Hercules”.  Because of this distance from earth, the global cluster is extremely hard to see with just the naked eye.  So to truly see the beauty in the cluster, one must use a telescope or binoculars to see it.  The linear size of the image is about 250ly across.

The cluster is made up of hundreds of thousands of stars coming together in the center to form a circular shape.  The stars are being pulled together towards the center by a gravitational pull.  This pull of gravity is not only true for The Great Cluster in Hercules, but also all other globular clusters.  In my image, you can see the stars being pulled together towards the center, yet you can also see how the gravitational pull is not as strong on the outer stars in the cluster.  In 1974, part of the Great Cluster was selected as one of the targets for one of the first radio messages that addressed the question of extra-terrestrial life outside of our planet.

In my picture, you can see the great amount of stars coming together to form the obvious center of the cluster.  Since I used a clear filter,and the picture does not have any color so it’s hard to tell which stars are the older or brighter ones.  The scientific content of my picture shows that gravity pulls stars together to form a semi-uniform circle pattern in the middle of the cluster.  Due to its size, and location in the constellation “Hercules”, The Great Cluster in Hercules is one of the most prominent and best known of all of the global clusters.  


Nemiroff, Robert and Jerry Bonnell. "M13: The Great Globular Cluster in Hercules" Astronomy Picture of the Day. 7 May 2007. Accessed 6 Dec. 2010. <>

Frommert, Hartmut, and Christine Kronberg. "Messier 13." Students for the Exploration and Development of Space. Accessed 3 Dec. 2010. <>.

Right Ascension (J2000) 16:40:17
Declination (J2000) +36:26:58
Filters used clear (C)
Exposure time per filter 300 seconds
Date observed

October 26, 2010

This photograph was done in Mosaic. Four different pictures were taken of the cluster than complied together to form this one photograph. All photos were taken the same night with the same filter and exposure time.



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