M41 was discovered by Giovanni Batista Hodierna sometime before 1654, although it was probably known to Aristotle as far back as 325 BC. If true, this would make it the faintest object recorded in classical antiquity, but caution prevails as Aristotle may have described a nearby part of the Milky Way instead. The cluster was catalogued by Charles Messier on January 16, 1765 and is best seen during the months of December, January and February from the tropics and Southern Hemisphere.
Appearing to the naked eye as a cloud like smudge, M41 is easily found with binoculars. In 10x50s, it appears as a large hazy blur with at least half a dozen stars resolvable. Larger 20x80 binoculars reveal many more stars spread across an almost circular shape. Through a small 100mm (4-inch) telescope at low magnifications, M41 is a beautiful sight with 50 or more stars visible against a mottled background. The stars appear to stream outwards from the centre of the cluster. A 150mm (6-inch) to 200mm (8-inch) scope reveals a loosely scattered multi-coloured cluster with many additional fainter members visible. Most of the stars appear white, but there are a few notable exceptions. These include a pair of bright yellow stars at the heart of the cluster with several red (or orange) giant stars interspersed. At high magnifications, M41 looks less cluster like, but the individual star colours are more intense.
M41 is estimated to be about 215 Million years old and is located 2,300 light-years from Earth. At the southeast edge of the cluster is 12 Canis Majoris, a blue-white B-type giant star with a mag. of +6.1. At only 668 light-years distant, this star is much closer to Earth and hence an interloper and not a true cluster member.
In total, M41 spans an area greater than that of the full Moon and contains about 100 stars with the brightest being of mag. +6.9. It's superb cluster, visible to the naked eye and and a wonderful sight in binoculars and telescopes.
M41 Data Table
|Object Type||Open Cluster|
|RA (J2000)||06h 46m 00s|
|DEC (J2000)||-20d 45m 15s|
|Apparent Size (arc mins)||39 x 39|
|Age (years)||215 Million|
|Number of Stars||100|
|Other Name||Collinder 118|