M13, or the Hercules Cluster, is one of the brightest globular clusters in the northern sky. A globular cluster consists of hundreds of thousands of stars held together by gravity. This particular cluster is several billion years old. It is named the Hercules Cluster because it is found in the Hercules constellation. The Hercules Cluster was discovered in 1714 by Edmond Halley, the man for whom Halley’s Comet is named.
All the bright dots in the picture are stars, and the bright region in the middle is a dense clump of stars. The clump is in the middle because that is the location of the center of gravity of the cluster. But not all stars are in the dense clump because some of the stars in the cluster are orbiting the center. The image above is about 250 light years in diameter, or about 60 times the distance from the Sun to its nearest star.
Nemiroff, Robert, and Jerry Bonnell. "M13: The Great Globular Cluster in Hercules". Astronomy Picture of the Day. Ed. Phillip Newman. 27 Apr. 2010. Web. 6 Dec. 2010. <http://apod.nasa.gov/apod/ap100527.html>.
Frommert, Hartmut, and Christine Kronberg. "Messier 13." Students for the Exploration and Development of Space. 21 Aug. 2007. Web. 6 Dec. 2010. <http://seds.org/messier/m/m013.html>.
|Right Ascension (J2000)||16:42:04|
|Filters used||clear (C)|
|Exposure time per filter||300 s|
October 26, 2010
This image is a Mosaic, created by combining 4 different photograph images of adjacent regions taken subsequently.