This is a dark nebula in the constellation Orion. The nebula is located just below (to the south of) Alnitak, the star farthest left on Orion's Belt, and is part of the much larger Orion Molecular Cloud Complex. The Horsehead Nebula is approximately 1500 light years from Earth. It is one of the most identifiable nebulae because of the shape of its swirling cloud of dark dust and gases, which is similar to that of a horse's head when viewed from Earth. The shape was first noticed in 1888 by Williamina Fleming on photographic plate B2312 taken at the Harvard College Observatory.
The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis.

This image is a cropped and 125% resampled version of this field.