M 50
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M 50

February 18, 2005
Open Cluster M50 (NGC 2323), type 'e', in Monoceros

Right Ascension: 07 : 03.2 (h:m)
Declination: -08 : 20 (deg:m)
Distance: 3.2 (kly)
Visual Brightness: 5.9 (mag)
Apparent Dimension: 16.0 (arc min)

Possibly discovered by G.D. Cassini before 1711. Discovered independently by Charles Messier in 1772.

This cluster was discovered on April 5, 1772 by Charles Messier, but possibly G.D. Cassini had already discovered it before 1711, according to a report by his son, Jacques Cassini, in his book of 1740, Elements of Astronomy.

Open cluster M50 is probably about 3,200 light years distant. Its angular diameter of about 15x20' therefore corresponds to a linear extension of about 20 light-years, the central dense part being only about 10' or 10 light-years in diameter. J.E. Gore, from photographic plates taken by Isaac Roberts in 1893, has estimated its population as about 200 stars in the main body. The cluster's Trumpler type is given as I,2,m (Glyn Jones), II,3,m (Sky Catalog 2000) or II,3,r (Götz). The visual appearance is described as a "heart-shaped figure" by Mallas and Kreimer.

According to Kenneth Glyn Jones, the brightest star is of spectral type B8 and mag 9.0, while the Sky Catalog 2000 gives spectral type B6 and mag 7.85, and the age is estimated as 78 million years. 7' south of the center is a red M giant, contrasting prominently against its blue-white neighbor stars. The cluster also contains some yellow giants.

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