Flame nebula, optical image. The flame shape is caused by a dark nebula. This cloud of dust and gas obscures the light from the emission nebula that lies behind, seen here as the red region at centre. The gas of this nebula glows as it is ionised by the radiation from hot stars. The bright star at lower right is Alnitak (Zeta Orionis), one of the three stars in Orion's belt, lying 817 light years from Earth. The nebula lies around 1500 light years away in the constellation Orion.