The sun is a favorite emblem of the middle ages, doubtless intended to show our LORD as the Sol Justitiae. Very frequently the Sun appears, surrounded by stars, on a vault or ceiling. On either side of the Crucifixion the sun and moon usually appear, more often than not with human faces.
The characteristics of the sun, as distinguished from the star, are the larger centre, and almost universally the alteration of straight and waved rays. The exception to this rule may be seen in the roses en soleil, which are drawn with straight rays.