SBIG ST-4000XCM14x600secDarks/Flats/Bias AppliedImager Temp -20C
Celestron 9.25 Reduced 0.63
20% CropCloudy Nights CCD Imaging Forum May Challenge WinnerAstrophotogallery.org May, 2009 Easy Category WinnerSky and Telescope Online Gallery June 1, 2009Messier 3
) is a globular cluster
in the constellation Canes Venatici
. It was discovered by Charles Messier
, and resolved into stars by William Herschel
around 1784. This cluster is one of the largest and brightest, and is made up of around 500,000 stars. It is located at a distance of about 33,900 light-years away from Earth
M3 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. Its apparent diameter of 18.0 arc minutes corresponds to a linear extension of about 180 light years.
Globular cluster M3 is extremely rich in variable stars:
By 1978, 212 variables have been found, 186 periods determined, more than in every other globular cluster in our Milky Way galaxy.
May 18, 2009