Horsehead nebula

The Horsehead nebula (also known as Barnard 33) is a dark nebula in the constellation Orion. 
The nebula is part of the much larger Orion complex. The nebula is located just to the south of the star Alnitak. Alniak is the farthest east on Orion's Belt. It is part of the much larger Orion Molecular Cloud Complex. 
Early history.
The nebula was first recorded in 1888 by Scottish astronomer Williamina Fleming. It was recorded on photographic plate B2312 taken at the Harvard College Observatory. The Horsehead Nebula is about 1500 light years from Earth. It is one of the most known nebulae because of its shape when seen from Earth. 
Composition of the nebula.
The dark cloud of dust and gas is a region in the Orion nebula where star formation is taking place. The nebula contains over 100 known organic and inorganic gases. It also consists of large and complex organic molecules.
The red or pinkish glow comes from hydrogen gas behind the nebula. Magnetic fields channel the gases leaving the nebula into streams that show as streaks in the background glow. A glowing strip of hydrogen gas marks the edge of the massive cloud. Thee densities of stars are different on either side. 
The darkness of the Horsehead is caused by thick dust blocking the light of stars behind it. The lower part of the Horsehead's neck casts a shadow to the left. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming.