M46

M46 is a rich, beautiful open cluster in Puppis, about 5,400 light-years from Earth. It contains roughly 500 stars spread across about 30 light-years, with an age of 300 million years. A planetary nebula (NGC 2438) appears projected against the northern edge of the cluster, creating a remarkable visual combination — though the nebula is likely a foreground object, not physically associated.

Located about 1 degree east of M47, making a wonderful contrasting pair. M46 appears as a large, misty patch in binoculars — much more granular and faintly textured than M47. A telescope at 80-100x resolves hundreds of faint, uniform stars. Look for the small ring of NGC 2438 (the planetary nebula) embedded in the northern edge — visible in 4-inch telescopes as a tiny round haze. Best observed from January through April.

Discovered by Charles Messier on February 19, 1771. The planetary nebula NGC 2438 within the cluster was discovered later by William Herschel. The question of whether the nebula is a true cluster member has been debated for decades.