The Horsehead Nebula (also known as Barnard 33' in bright
nebula IC 434) is a dark nebula in the Orion constellation.
The nebula is located just below Alnitak, the easternmost
star of Orion's Belt, and is part of the much larger Orion
Molecular Cloud Complex. It is approximately 1,500 light
years from Earth, and is approximately 3.5 light years wide.
One of the most identifiable nebulae in the sky, it 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 by Mrs.
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.
(From
Wikipedia, the free encyclopedia)
