Four degrees due south of Sirius, you’ll find the fine open star cluster M41. With a mix of hot blue-white stars and a few red giants, this cluster presents a range of contrasting color and brightness. In dark skies, you can see Messier 41 with the naked eye. But it looks best at low power in a modest telescope or pair of binoculars. It’s primed for viewing in the late evening this time of year.
• M41 is a fairly loose open cluster. It’s easy to resolve in a small telescope and spans the same area as the full Moon.
• To get the most pleasing view of M41, keep the magnification as low as possible. It’s especially pretty in binoculars at 10x-15x; you’ll see 40 or 50 stars in a 3-inch or larger telescope at 25x to 40x. More stars will be revealed at higher magnification, but you’ll lose the aesthetic beauty of the cluster.
• Altogether, M41 is a bright object of magnitude 4.6, and is easy to find just 4 degrees south of Sirius in the constellation Canis Major. This is a fine region for bright nearby stars. Just west of Sirius is Mirzam, a star in Canis Major which 4 million years ago far outshone Sirius as the brightest star in our sky. Mirzam’s brightness changes in a complex way, with beats and harmonics that oscillate like slightly out-of-tune guitar strings.
Messier 41 in Canis Major
• M41 contains mostly young blue-and-white stars. But near the center of the cluster, look for a contrasting deep orange red star of ninth magnitude. Within the field of view of a low-power eyepiece, you’ll also see the bright 6th magnitude star 12 Canis Majoris.
• M41 is best positioned for those of you in the Southern Hemisphere where it’s an easy naked eye object. But it’s not to hard to find in the northern hemisphere either. If you can see Sirius, chances are you can see M41.
• Physically and scientifically there is nothing remarkable about M41. It’s 2,300 light years away and spans some 25 light years. This cluster is of a modest age, some 100 million years old. But it’s still a fine object for modest telescopes and well worth a look from anywhere in the world, whether you’re in Paris, Portland, or Perth.
Bit of History
The great Aristotle was possibly the first to note this cluster in 325 B.C.
I’ve often heard amateur astronomers talk about the beauty of M41. But for me, it’s usually lost in the murk near the southern horizon, so I’ve never had a great view of it. I’ve settled for the pretty and better-positioned open clusters of Auriga: M36, M37, and M38. All these open clusters look beautiful against a velvety black midwinter sky.