Orion nebula, optical image. The Orion nebula can be seen with the naked eye as a fuzzy patch in the constellation Orion. It comprises several nebulae, but the brightest is M42 pink, upper left. M43 is the small round pink nebula immediately below M42. These nebulae glow pink as the hydrogen they contain is ionised by radiation from hot young stars that recently formed inside them. In the case of M42, the stars that light it up are a group of four known as the Trapezium upper centre. The blue nebula NGC 1977 is at lower centre. This nebula is not ionised, instead reflecting the light of nearby blue stars. The nebulae lie around 1500 light years from Earth.