Located just below Alnitak, the easternmost star of Orion's Belt, the Horsehead Nebula
is part of the much larger Orion Molecular Cloud Complex. It is approximately
1,500 light years from Earth and 3.5 light years wide.

One of the most identifiable nebulae in the sky, the Horsehead Nebula
is part of a swirling cloud of dark dust and gases, shaped like a
horse's head (hence its name). Also known as Barnard 33, the unusual
shape was first discovered in 1888 on a photographic plate taken at the
Harvard College Observatory.

The red glow (the bright area in this monochromatic image)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.