M41

Messier 41, designated M41 or NGC 2287, is an open star cluster in the southern constellation Canis Major. It is one of the brighter open clusters in the Milky Way and is visible to the naked eye under dark-sky conditions.

The cluster was reportedly observed by Giovanni Batista Hodierna before 1654 and was later cataloged by Charles Messier in 1771 as M41. It is also listed in the New General Catalogue as NGC 2287.

M41 lies in Canis Major near the bright star Sirius, in the plane of the Milky Way. It lies roughly 4,000 light-years from Earth (about 1,200 parsecs) and has an apparent magnitude around 4.5. The cluster spans about 25 arcminutes on the sky, corresponding to a physical size of roughly 25–30 light-years.

M41 is a relatively rich open cluster, with on the order of 100 to 150 confirmed members. Its age is estimated at a few hundred million years, placing it among mid-aged open clusters. The cluster contains a mix of hot blue stars and cooler yellow-red members, which contribute to its visible richness.

Observationally, M41 is well studied and serves as a reference for investigations of stellar evolution and the structure of the Galactic disk. It is best observed with binoculars or a small telescope, which reveal a dense bouquet of stars; larger instruments resolve many faint members and provide more detailed cluster structure.