Here is an example of an emission nebula. This is the Rosette Nebula in the constellation Monoceros (mo-nos-er-os). The nebula surrounds a young star cluster. This nebula is emitting its own light, due to the presence of ultraviolet radiation from the very hot young stars that make up the cluster. This radiation, although not visible to the eye, is strong enough to 'excite' the atoms in the interstellar dust and gas so that they 'jump' to different energy levels and emit their own form of radiation which can be seen in the nebula's light spectrum. It is not simply reflecting the light from the cluster. Emission nebulae can be found in many areas of the night sky, the most famous being the Orion Nebula. In astronomical terms, these type of nebulae are also referred to as H II regions (H two). This is because of the hydrogen atoms having been ionized - gaining or losing its single electron due to the strong ultraviolet radiation from a star or stars.