The 'Sword of Orion' contains a few of the most beautiful nebulae in the sky: NGC 1977 ( 'Running Man Nebula') to the left, small M43in the middle, and last -but not least - M42, the 'Great Nebula in Orion'. All of them shine in the spectral emission line of hydrogen and oxygen.
The whole complex is embedded in a huge hydrogen cloud, visible dimly red. The 'Trapezium' in the middle of the small bright patch in M42 has caved out a big hollow shell by its radiation, which excites the inner walls to glow brightly.