SBIG ST-4000XCM
14x600sec
Darks/Flats/Bias Applied
Imager Temp -20C
Celestron 9.25 Reduced 0.63
20% Crop

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Messier 3 (NGC 5272) is a globular cluster in the constellation Canes Venatici. It was discovered by Charles Messier in 1764, 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