“Horsehead Nebula”-RGB

The Horsehead Nebula (also known as Barnard 33 in emission nebula IC 434) is a dark nebula (opens in a new tab) in the constellation Orion (opens in a new tab). The nebula is located just to the south of the star Alnitak (opens in a new tab), which is furthest east on Orion’s Belt, and is part of the much larger Orion Molecular Cloud Complex (opens in a new tab). The Horsehead Nebula is approximately 1500 light years (opens in a new tab) 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 (opens in a new tab)'s head when viewed from Earth. The shape was first noticed in 1888 by Williamina Fleming (opens in a new tab) on photographic plate B2312 taken at the Harvard College (opens in a new tab) Observatory. The red glow originates from hydrogen (opens in a new tab) gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis (opens in a new tab). 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 (opens in a new tab). Bright spots in the Horsehead Nebula’s base are young stars just in the process of forming.