IC 434, the Horsehead Nebula.

The Horsehead Nebula (also known as Barnard 33 or IC 434) is a dark nebula in the Orion constellation. The nebula is located just below Alnitak, the easternmost star of Orion's Belt.

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 on a photographic plate 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. Light takes about 1500 years to reach us from the Horsehead Nebula.

External links

• The Horsehead Nebula @ The Electronic Sky
• Hubble Observes the Horsehead Nebula