Rosette Nebula ( NGC2237 ) Colors processed with the Hubble SHO palette. The synthetic color image is a SHO palette modified through the Ha, SII and OIII data. The chromatic contrast of the three emission lines in this SHO version shows us how different components are combined and mixed.

The Rosette Nebula, also known as Caldwell 49, is a large, circular HII region. It lies at the edge of a huge molecular cloud in the constellation Monoceros. The open cluster NGC 2244 (which can be seen at the center of the nebula) is associated with the nebula, as this star cluster has formed through the nebula’s matter. The nebula and cluster are 5,200 light-years from Earth and the size of the nebula is estimated to be around 130 light-years in diameter. The radiation from the young stars excites the atoms in the nebula, causing them to emit radiation that makes the nebula glow. It is believed that the stellar wind from stars O and B exerts pressure on the entire cloud, causing its compression and the formation of stars in the nebula.

The Rosette Nebula complex is described through several objects in the NGC catalog: NGC 2237 (part of the nebula and is also used to describe the entire nebula), NGC 2244 (open cluster in the center detailed above), NGC 2238 (part of the nebula), NGC 2239 (part of the nebula) and NGC 2246 (part of the nebula).