The Horsehead and the Flame Nebula in Orion
The Horsehead Nebula and the neighbouring Flame Nebula are some of the most iconic objects to adorn the winter night sky in the constellation of Orion located close to Alnitak, the easternmost of the three stars that make up Orion’s Belt. These nebulae are part of the Orion Molecular Cloud Complex, which are giant interstellar clouds of hydrogen gas in which new stars are observed to develop. In a nutshell, when one observes these nebulae in the night sky, one is watching the closest stellar nurseries in action. Another famous nebula within this stellar nursery is the Great Orion Nebula located just to the south-east. Both the Horsehead and Flame Nebulae are a cosmic stone’s throw away at about 1350-1375 light years from Earth. Being a classic example of a dark nebula, the Horsehead Nebula derives its name from the dark silhouette vividly resembling a horse’s head and neck against the background red glow of the hydrogen gas. This is mainly due to dense dust and gas in the active star-forming region blocking the light emanating from the hydrogen gas clouds in the background. Protostars in the process of development are invisible in the visible wavelengths of light, thereby shrouding them behind the dust. Note the streaks faintly visible in the background nebula behind the Horsehead Nebula, this is a direct result of the star sigma Orionis channelling ionised hydrogen gas to align with its magnetic flux. The neighbouring Flame Nebula derives its name from its visual resemblance to a burning flame. The ultraviolet light from nearby blue supergiant star Alnitak knocks electrons off from the hydrogen gas clouds nearby, causing them to shine in red when those electrons recombine with the ionised hydrogen. X-ray observations of this nebula reveals that 80% of its new-born stars possess circumstellar disks, which are breeding grounds for new planets and potentially, life to form.