Horsehead Nebula, dark nebula located in the constellation Orion; designated IC 434 or B 33. It consists of a cloud of nonluminous interstellar matter resembling the outline of a horse's head and appears against the background of a bright emission nebula. The Horsehead Nebula measures about 4 min of arc at its greatest width. It is located near the belt of Orion at a distance of about 1,600 light-years from the earth.
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