posted by Vern
on Sat Apr 4, 2009 12:03 pm MDT
Located just over 5 degrees south of the 3.9 magnitude star Alpha Monoceres in the northern region of the constellation Puppis is Messier 46.
M46 is a beautiful open cluster containing around a 150 stars from 9th to 13th magnitude in a 25 arc minute wide field.
Just north of the center of the richest cluster of stars is planetary nebula NGC 2438. Although the planetary nebula appears embedded in the field it is unrelated. The nebula is super-imposed on the 1380 parsecs (4500 light year) distant star cluster.
Image credit: Brian Kimball, Longmont Astronomical Society
Note - if you are interested in observing some open clusters first hand, you might check out the Astroleague's Open Cluster Observing Club