Subsun and Halo

March 04, 2003


Provided by: James Kaler, Astronomy Department, University of Illinois
Summary authors & editors: James Kaler

As the audience looks out through the window of a high-flying airplane, dancing ice crystals mount a variety show on the stage of the sky. Sunlight refracted through randomly oriented, hexagonal crystals in the clouds forms the lower part of the 22-degree halo, which is centered around the Sun (off the top of the photo). Down below is a bright subsun caused by reflection from the crystals' upper surfaces. Pencil-shaped crystals floating more or less parallel to the ground create a faint elongated enhancement at the bottom of the halo, connecting these phenomena.

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