M46 - NGC 2437

Messier 46 (NGC 2437) is a rich and attractive open cluster in the constellation Puppis, located approximately 5,400 light-years from Earth. It contains roughly 500 stars within a diameter of about 30 light-years and shines at a combined apparent magnitude of about 6.1. The cluster is estimated to be around 300 million years old. M46 was discovered by Charles Messier on February 19, 1771, on the same night he also found the neighboring cluster M47. The most striking feature of M46 is the planetary nebula NGC 2438, which appears projected onto the northern edge of the cluster. This small, ring-shaped nebula is about 1 arcminute in diameter and is visible in telescopes of 6 inches or more as a tiny, ghostly ring among the cluster stars. However, despite its apparent association, NGC 2438 is now believed to be a foreground object at a different distance from M46 and is not physically related to the cluster. The coincidental alignment nonetheless creates one of the most unique and photogenic combinations in the deep sky. M46 itself is a beautiful object through a telescope, presenting a dense, uniform field of similarly bright stars that gives it an almost sparkling, granular texture. The cluster spans about 27 arcminutes, nearly the size of the full Moon, and contains very few bright stars, so the overall impression is of a shimmering carpet of faint stellar points. M46 and M47 lie only 1.5 degrees apart and make an excellent contrasting pair: M46 is rich, dense, and composed of faint stars, while M47 is sparse, bright, and scattered. Both fit in a single binocular field of view.

Contains approximately 500 stars within 30 light-years diameter at a distance of 5,400 light-years, spanning 27 arcminutes at magnitude 6.1.