The iconic Horsehead Nebula is a beautiful dark nebula located 1600 light years away in the constellation of Orion. It is the most recognized dark nebula in the sky because of the shape of its swirling cloud of dark dust and gases, which bears resemblance to a horse's head when viewed from Earth. The nebula lies in a field of rich objects which, on their own, would each be the star of the show. But here the Horsehead steals the attention from all of them.
The dark cloud of IC 434 is a region in the Orion Molecular Cloud Complex where star formation is taking place. One newly formed star is visible on the horse’s brow. The nebula spans 5 arc-minutes in our apparent view. This corresponds to a width of 2 light years.
The nebula's reddish glow is from hydrogen gas behind the nebula, ionized by the nearby bright naked-eye star cluster Sigma Orionis just above the Horsehead. Magnetic fields steer the gases into streams, shown in the image as vertical streaks in the background glow.
As annotated in image revision F, the other wonderful objects in the same view, from left to right, are:
- At the left image edge, the beautiful textured red glow of IC 432 (together with the blue haze of vdB 51).
- Just to the right of IC 432, the bright star Alnitak, a triple star system whose main star is 20x the diameter of our sun.
- Just below Alnitak, the fascinating dust lane structure of the Flame Nebula (NGC 2024).
- Just to the right of the Flame, the colorful reflection nebula NGC 2023 (also known as LBN 954). Like the Horsehead, this nebula is 4 light years across.
- The blue glow of IC 435 at the bottom center of the image.
Several small bright red comma-like Herbig-Haro objects are seen in the lower half of the image. 3 of the most visible are:
- HH249, seen just below and left of the Horsehead.
- HH94, seen to the right of IC435
- HH95, seen below and right of HH94
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