Paranal, Chile Sunset

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A remarkable double sunset mirage at Paranal Observatory high in the Atacama Desert, Chile . Astronomer Luc Arnold of Observatoire de Haute-Provence, France saw this spectacular apparition in January 2002 at the site of the European Southern Observatory Very Large Telescope array of four 8.2 meter reflectors. He was at an altitude of 2,400 meters as the sun set over the Pacific Ocean whose shore was 12 km away.

The upper, very bright, image is a very highly flattened sun setting through a strong inversion layer. The layer is visible as a hazy band each side of the sun.

Details below this layer are partially hidden by the band of marine stratus cloud which is capped by the upper inversion. The puzzle is the relatively undistorted second erect image of the sun setting into the ocean horizon below the clouds. At Paranal's altitude, this sea horizon (including refraction effects) might be more than 80 miles distant and well below the astronomical horizon. To explain the lower sun we must invoke a second, lower and stronger inversion layer. This produces the lower erect image and possibly parts of an inverted image hidden by the clouds. The lower image is less distorted than is usual in mock-mirages because it is viewed considerably below the astronomical horizon and the rays therefore pass through the air layers less 'edge-on'. My thanks to Andrew Young for this analysis.

Images ©Luc Arnold, shown with permission.