Messier 50, NGC 2323

Messier 50, or NGC 2323, is a bright open cluster in Monoceros, near its border with Canis Major.

M 50 was discovered in 1710 by Cassini, the famous observer of Saturn; Charles Messier rediscovered it in April of 1772 while observing a prominent comet.

M 50 is an impressive cluster of magnitude 5.9, visible in binoculars as a bright concentration of stars. It contains 200 members, of 8th magnitude and fainter, in an area about 15' x 20' in diameter. There is a string of stars in the north-south direction, and a rich heart-shaped concentration at the center, offset by a starless void to the north.

A red giant 7' south of the center contrasts prominently against its blue-white neighbor stars. The cluster also contains some yellow giants. There is no background nebulosity.

M 50 has a diameter of about 12 light-years, and is about 3,200 light years away. The cluster's age is estimated as 78 million years, and its brightest star is of spectral type B8.