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Globular Cluster in Scorpius

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Messier 4 is one of the easiest globular clusters to locate. It is just 1.3 degrees due west of Antares, the red first magnitude star in Scorpius that is very prominent in the southern sky on summer evenings. It is easy to spot with binoculars. Through a telescope, one distinct feature is the row of bright stars running from north to south through the center of the cluster (which is more obvious through the eyepiece than it appears in this picture).

This cluster is noteworthy for a few reasons. At a distance of about 6800 light years, it is one of the closest globular clusters.  Compared to other bright globular clusters, it is fairly small and contains fewer stars. Messier 4 may contain something like 10,000 stars, whereas some of the larger globular cluster contain 500,000 or more stars. This difference in both the number of stars and their density is pretty obvious if you compare this image to my pictures of Messier 3 or Messier 13.

Magnitude 5.9
Apparent Size 26'
Distance (light yrs) 6,800
Right Ascension 16:23.6
Declination -26 32

Image details:  Exposure times of 22 minutes luminance and 6 minutes each of red, green, and blue, taken with an SBIG ST-8300M imager and a 14" Meade LX850 telescope at f/6.

May 2014