The Rosette Nebula (NGC 2237–39, 2244) is a large H II region and stellar nursery about 5,200 light‑years away in the constellation Monoceros. Spanning roughly 100 light‑years, it consists of a central cavity surrounded by ionized gas illuminated and sculpted by the young star cluster NGC 2244, with pillars, cavities, and ongoing star formation.
Source: science.nasa.gov
22/08/2000

In the heart of the Rosette Nebula lies a bright open cluster of stars that lights up the nebula. The stars of NGC 2244 formed from the surrounding gas only four million years ago and emit light and wind that define the nebula's appearance today. High energy light from the bright young stars of NGC 2244 ionizes the surrounding hydrogen gas clouds to create the red emission nebula appearance. The hot wind of particles that streams away from the cluster stars contributes to an already complex menagerie of gas and dust filaments while slowly evacuating the cluster center. NGC 2244 measures about 50 light-years across, lies about 4500 light-years away, and is visible with binoculars towards the constellation of Monoceros.