National Geographic : 1959 May
The turbulent Great Nebula in Orion suggests an inferno such as Dante had in mind. But no fires light this frightful scene. Celestial "flames" are gases fluorescing under the stimulus of hot stars near by. Blue reveals a high proportion of oxygen; red indicates a predominance of hydrogen, the pri- Cosmic Smoke Ring Encircles a Hot Star The Ring Nebula in Lyra, a familiar sight to amateur astronomers, appears relatively colorless through the telescope because the eye cannot de tect colors at low light intensities. But high speed color film, which accumulates light in a way the eye cannot, reveals this astronomical gem in all its prismatic beauty. Although nebular gases appear dense, they are incredibly rarefied. This ring, with only a thou sand atoms of gas per cubic centimeter, far sur passes most vacuums attainable on earth. A very hot blue star centered in the ring bom bards the gases with invisible ultraviolet rays. Fluorescing gases convert the energy to visible light. Colors vary according to their distance 674 from the source of energy.