Rosette Nebula
In astronomy, the Rosette Nebula is a large, circular emission nebula located near one end of a giant molecular cloud in the Monoceros constellation.
Embedded in the center of the Rosette Nebula is an open cluster. The blue stars in this cluster, labelled NGC 2244, emit ultraviolet light that knocks electrons away from hydrogen atoms. When the electrons fall back, they emit the red light seen here. The Rosette Nebula is about 100 light-years across.
Larger version
It is believed that stellar winds from a group of O and B stars are exerting pressure on interstellar clouds to cause compression, followed by star formation in the nebula.
The Rosette Nebula has an angular diameter of 1.3° and lies some 900 parsecs or 3000 light years from Earth's Solar System.
