This plume of dark material makes up one of the most recognisable objects in the night sky - the Horsehead Nebula in Orion. The horsehead shape is visible against the glowing pink of the emission nebulaIC 434.
The Horsehead is in fact a small segment of the immense Orion Molecular Cloud, formed from a tendril of gas and dust that stands out against the pale pink glow of a swathe of ionised hydrogen within the Cloud, itself designated IC 434. This dark strand of matter has a twist at its tip, folding back on itself in a way that creates the distinctive horsehead form from which the nebula takes its name.
A dense accumulation of material, this nebula creates a region in which new stars are being formed, especially in the denser regions that form the 'neck' of the horse's head.
A view of the sky around the Horsehead Nebula. The dark shape of a horse's head in the centre of this image is silhouetted against the pale nebulaIC 434. The whole complex lies southward of the Alnitak, the eastern star of Orion's Belt. Imagery provided by Aladin sky atlas