101 Must-See Cosmic Objects: The Rosette Nebula

Observers and astroimagers usually think of the magnificent Rosette Nebula as a single deep-sky object. But actually, this combination of a star cluster and nebula has five separate entries in the New General Catalogue: NGC 2237, NGC 2238, NGC 2239, NGC 2244, and NGC 2246. And although they all lie within the constellation Monoceros the Unicorn some 5,200 light-years away, they weren’t all discovered at the same time.

The beautiful open cluster NGC 2244, which lies at the center of the n