The Horsehead Nebula is a dark nebula in the Orion constellation. The nebula is located just below Alnitak, the left star of Orion's Belt. 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.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.
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