Tuesday, April 26, 2011

ESO Image: Rare green flash on the moon

A rare green flash on the moon is captured by ESO Electronics Engineer Gerhard Hudeepohl using European Southern Observatory's Very Large Telescope in Chile.

The effect is caused by the Earth's atmosphere bending or refracting light. The effect is greater in the lower, denser layers of the atmosphere.

ESO explains: "Shorter wavelengths of light are bent more than longer wavelengths, so that the green light from the Sun or moon appears to be coming from a slightly higher position than the orange and red light, from the point of view of an observer.

When the conditions are just right, with an additional mirage effect due to the temperature gradient in the atmosphere, the elusive green flash is briefly visible at the upper edge of the solar or lunar disc when it is close to the horizon."

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