Emission nebula. Optical image of the emission nebula IC 2177. Part of the nebula NGC 2327 is seen at bottom left. IC 2177 is a huge cloud of gas (mainly hydrogen) which glows as it is ionised by ultraviolet radiation from hot young stars embedded within it. A prominent dark dust lane is seen in silhouette, which blocks the light from the bright nebula behind it. This nebula lies in the constellation Monoceros.