Heiligenschein (German for "aureola" , literally "saint's shine", pronounced [ˈhaɪlɪɡənˌʃaɪn]) is an optical phenomenon which creates a bright spot around the shadow of the viewer's head. It is created when the surface on which the shadow falls has special optical characteristics. Dewy grass is known to exhibit these characteristics, and creates a Heiligenschein. Nearly spherical dew droplets act as lenses to focus the light on the surface beneath them. Some of this light 'backscatters' in the direction of the sunlight as it passes back through the dew droplet. This makes the antisolar point appear the brightest.
The opposition effect creates a similar halo effect, a bright spot of light around the viewer's head when the viewer is looking in the opposite direction of the sun, but is instead caused by shadows being hidden by the objects casting them. When viewing the Heiligenschein, there are no coloured rings around the shadow of the observer, as in the case of a glory.