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Astr110 Photography Projects, Spring 2008

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Globular Cluster (M92), Jenn VandenAkker

Globular Cluster

Globular clusters are concentrations of ten thousand to one million stars that are bound together by gravity. They can spread over a diameter of ten to two hundred light years. Abrahim Ihle was the first to discover a globular cluster: he discovered M22 in Sagittarius in the year 1665. Ihle and others who discovered these clusters after him thought they were nebulas. It was not until 1782 when William Herschel coined the term "globular cluster." Globular Cluster M92 is one of the brighter clusters and second brightest in its constellation, Hercules. It was discovered by Johann Elert Bode on December 27, 1777; cataloged by Charles Messier on March 18, 1781; and classified as a "globular cluster" by Herschel in 1783.

Globular Cluster M92 is visible to the naked eye under excellent conditions. It has an estimated distance of 26,000 light years and an angular size of approximately 14.0 arcminutes, which corresponds with its diameter of 109 light years. It also has a mass of up to 330,000 suns. Additionally, it is approaching Earth at 112 km/sec. This cluster is often overlooked because of being so close (9.5 degrees northeast) to the slightly brighter M13.

References:

Frommert, Hartmut and Christine Kronberg. "Messier 92." <http://www.seds.org/messier/m/m092.html>

Frommert, Hartmut and Christine Kronberg. "Globular Star Clusters." <http://www.seds.org/messier/glob.html>

"M92, The Forgotten Globular Cluster in Hercules." Celestron Images. <http://www.celestronimages.com/details.php?image_id=2136>

Right Ascension (J2000) 17:17:60
Declination (J2000) 43:08:00
Filters used blue(B), green(V), red(R), and clear(C)
Exposure time per filter 5x60 seconds in all filters
Date observed

March 24, 2009, 7:29:52 EDT