Red Air Glow over Chile

RED AIRGLOW OVER CHILE: On Sept. 1st, astrophotographer Yuri Beletsky hiked into the Atacama Desert of Chile for a deep exposure of the Milky Way. He got that and much more. "There was a stunning display of red airglow," he says. It surrounded the Milky Way like a celestial bulls-eye:

Airglow is aurora-like phenomenon caused by chemical reactions in the upper atmosphere. Human eyes seldom notice the faint glow, but It can be photographed on almost any clear dark night, anywhere in the world.

The curious thing about Beletsky's photo is not the presence of airglow, but rather its color--red. Airglow is usually green, the color of light from abundant oxygen atoms in a layer 90-100 km high. Where does the red come from? Instead of oxygen, less abundant hydroxyl ions (OH-) can produce the required color. These ions exist in a thin layer 85 km high where gravity waves impress the red glow with a dramatic rippling structure.

"It was a truly special night," says Beletsky. "Pure tranquility."

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