Heiligenschein

'halo, aureola') is an optical phenomenon in which a bright spot appears around the shadow of the viewer's head in the presence of dew.

In photogrammetry and remote sensing, it is more commonly known as the hotspot.

[1] Nearly spherical dew droplets act as lenses to focus the light onto the surface behind them.

This configuration is similar to a cat's eye retroreflector.

When dew droplets are suspended on trichomes at approximately this distance away from the surface of a plant, the combination of droplet and plant acts as a retroreflector.