Star Clusters M3 - Globular Cluster Previous Enlarge to Full Size Date: 5/20/2005 M3 in the constellation Canes Venatici is one of the most outstanding globular clusters, containing an estimated half million stars. At a distance of about 33,900 light years, it is further away than the center of our Galaxy, the Milky Way, but still shines at magnitude 6.2, as its absolute magnitude is about -8.93, corresponding to a luminosity of about 300,000 times that of our sun. M3 is thus visible to the naked eye under very good conditions - and a superb object with the slightest optical aid. Its apparent diameter of 18.0 arc minutes corresponds to a linear extension of about 180 light years M3 has a compressed, dense core measuring 1.1' in diameter, or linearly, 11 light years, comparatively large for a globular. Its half-mass radius is 1.12', or about 11.2 light years, so that half of this clusters mass is contained in a volume of only 22 light years in diameter. 1st Light with the SBIG St-8i May 20, 2005 - 2 days before full moon Toronto, Canada 8" LX200GPS @ f/10 SBIG ST-8i Baader Neodymium Sky Glow filter 15 x 20sec average combined/dark subtracted No flats CCDSoft, K3CCDTools, PixInsight, Photoshop

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