Orion nebula. Optical image of the Orion Nebula in the constellation of Orion. This nebula is around 1500 light years away from Earth, and consists of M42 (the main part) and M43 (the smaller round nebula above M42). M42 and M43 are clouds of dust and gas, mainly hydrogen, which are ionised and lit up by the Trapezium Cluster of hot, young stars (not seen) situated in the brightest region at the centre of the nebula. Orion's belt is a distinctive group of three stars in a straight line (upper centre). The furthest left of these, Alnitak (zeta Orionis), is also surrounded by red nebulosity. Orion is a prominent constellation straddling the celestial equator. North is at top.