Rosette Nebula

The Rosetta Nebula (also known by its catalogue designations NGC 2237 and C 49) is a large, crudely circular H II region located at the edge of a giant molecular cloud in the constellation Monoceros.

The nebula has an angular diameter of 1.3° and is located at a distance of 1600 parsecs (about 5200 light-years) from the Solar System; It has an approximate size of 100 light-years.

At the centre of the Rosetta Nebula is a bright open cluster, known as NGC 2244; the blue stars of the cluster, part of the OB association known as Monoceros OB2, emit ultraviolet radiation, which excites the gas of the nebula causing it to emit red light. The stellar wind from the O and B group of stars is thought to exert pressure on the interstellar cloud causing compression, followed by star formation; in fact, many Bok globules have been observed in the region, believed to be the site of star formation.