NGC 2237, the Rosette Nebula, is a very large star-forming nebula located in the constellation of Monoceros approximately 5000 light-years from the Earth. At the center of the nebula is a cluster of newly formed, very massive, type O stars. These huge stars, with their intense radiation and stellar winds, have swept a large cavity in the center of the Rosette nebula. In the image above, a portion of this stellar cavity is visible. Surrounding the cavity are columns of dust and gas along with more tenuous clouds of gases. These gases are excited by the intense radiation from the central massive stars causing the nebula to glow.
The image above was assembled from three narrowband filtered images. These consisted of SII mapped to red, Ha mapped to green, and OIII mapped to blue. The Ha filtered image was also used for the luminance channel. The resulting image is a false color image using the standard Hubble pallet.