The Horsehead Nebula (also known as Barnard 33 in emission nebula IC 434) is a dark nebula in the constellation Orion. The nebula is located just to the south of the star Alnitak, which is farthest east 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. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead’s neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula’s base are young stars just in the process of forming.
Exposures: 10x1800s H-alpha (horsehead), 11x600s H-alpha (flamenebula)