Orion nebula. True-colour optical image of the great Orion nebula (M42 & M43, pink, with NGC 1977 above) showing the fine strands of nebulosity in its outer reaches. These nebulae lie around 1500 light years away in the constellation Orion. M42 and M43 are HII regions, areas of gas (mainly hydrogen) and dust where newly born stars excite the gas, causing it to glow. M42 and M43 are excited by a group of stars (the Trapezium) embedded in them. The stars are here obscured by the bright central region. NGC 1977 is a reflection nebula, which reflects the light of stars embedded in it. These typically appear blue as blue light is scattered more than red.