NGC 2237, the Rosette Nebula in Monoceros, is located 5,000 light-years away.

It is 130 light-years across and the central "hole" is 50 light-years in diameter.

The Rosette is a large complex of bright emission nebulosity and dark nebulae that is a star forming region that is more than one degree in apparent diameter.

The star cluster in the middle of the Rosette is NGC 2244 with six bright 6th, 7th and 8th magnitude stars that look like a ladder. The cluster's visual magnitude is 4.8 and it can be seen with the unaided eye. In the original NGC descriptions, NGC 2239 referred to the cluster.

Brighter parts of the Rosette nebula are labeled NGC 2237, NGC 2238 and NGC 2246, but the entire nebula is usually referred to as NGC 2237.

Stars in the cluster inside the Rosette formed out of the dust and gas in the region of the Rosette Molecular Cloud (RMC) three to four million years ago. The stellar winds from these hot young OB stars has cleared out the cavity in the center of the nebula. The ultraviolet light from these stars causes the hydrogen gas in the region to glow with the characteristic red color of an hydrogen-alpha emission nebula.

Different parts of the Rosette were discovered by different observers. The open cluster, NGC 2244, was discovered by John Flamsteed in 1690, and William Herschel in the 1890's. NGC 2238 was discovered by Albert Marth in 1864. NGC 2239 was discovered by John Herschel in 1830. NGC 2237 and NGC 2246 were discovered by Lewis Swift in 1871 and 1885 respectively.

The dark nebulae in this photo are part of a complex of Bok globules inside of the Rosette Nebula. Bok Globules are dense opaque clouds of dust and gas, some of which are condensing under gravitational attraction to form stars and planets. The globules are named after astronomer Bart Bok, who observed them in the 1940's.

An easy way to find the Rosette is to start at Meissa (Lambda Orionis) and draw a line to Betelgeuse (Alpha Orionis) and extend it 7.5 degrees to 4.4 magnitude 8 Monoceros. Then go 2 degrees farther to the east-northeast to hit the Rosette. It will be easily visible in a finder or binoculars.

North is to the top in the above image.

NGC 2237 Catalogs: NGC 2237 Common Name: Rosette Nebula Object Type: Cluster and Nebula Magnitude: Cluster: 5.5 Size: Nebula: 80' x 60', Cluster: 24' Constellation: Monoceros Image Field Centered At: RA: 06h 32m 01s Dec: +04° 55' 17"