NGC 2023 & IC 434

IC 434, known as Barnard 33 and the Horsehead Nebula, and the reflection nebula, NGC 3023, are located in the constellation of Orion, around 1,500 ly from Earth. The Horsehead nebula is part of a large, dark, molecular cloud and first discovered on a photographic plate in the late 1800s. 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 funnelled by a strong magnetic field.
NGC 2023 is one of the largest reflection nebulae in the sky, discovered by William Herschel on January 6, 1785. It is illuminated by a massive young star, HD 37903.