Ice crystals cause light dance Double sun over Meßdorfer Feld

Bonn · Valens Mulindabigwi took this impressive photo on Sunday afternoon while walking across Meßdorfer Feld. A sundog can be seen beside the setting sun as a result of a so-called halo event.

Halo is the collective term for atmospheric optical light effects, which result from the reflection and refraction of light on ice crystals. They are light spots which are seen around 22 degrees to the left or right, or sometimes on both sides, of the sun. Depending on the size and position of the ice crystals as well as the angle at which the light hits the crystals, partly white, partly coloured circles, arcs, columns or light spots are created at various points in the sky.

The observer has the impression that next to the sun there is a second, weaker one. In English they are called sundogs, because they accompany the sun. Sundogs are one of the most frequent halos. Although sundogs often have colours reminiscent of rainbows, they should not be confused with them.

Sundogs appear close to the sun, rainbows appear on the opposite side of the sky to the sun. In the case of rainbows, water droplets are the cause of the optical effect and in the case of Sundogs, ice crystals, which refract or reflect the sunlight.

Original text: Jürgen Pohlmann. Translation: kc

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