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Object description |
Messier 23 (NGC 6494) is one of the brighter open star clusters in the constellation Sagittarius. It lies at a distance of 2200 light-years from the solar system, about halfway to the Sagittarius Arm of our Milky Way. Only a few degrees east lies the center of the Milky Way. With a total brightness of the 5.5th magnitude class, it is visible to the naked eye under dark skies.
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It
contains about 150 stars starting with the 10th magnitude class. The apparent
size in the sky covers just under 27 arcminutes, about the size of a full moon
seen with the naked eye. This gives a physical diameter of 15 to 20 light-years
for a distance of 2200 light-years. The star cluster has an estimated age of
300 million years and it is assigned to class III 1
m according to Trumpler. The star cluster was discovered June 24, 1764 by Charles Messier. « Click here or the thumbnail to load a large annoted image. |
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