Glory (optical phenomenon)

NASA photo

A glory is a rainbow in the shape of a circle. Because one of the requirements for observing this optical effect is a shadow cast onto a cloud or mist layer, it is most commonly observed while airborne, for example as created by an airplane's shadow on clouds. They can have the same double structure as regular rainbows.

A historical name for this phenomenon is the Brocken Specter or Specter of the Brocken. The name derives from the Brocken, the tallest peak of the Harz mountain range in Germany. Because the peak is above the cloud level, and the area is frequently misty, the condition of a shadow cast onto a cloud layer is relatively favored. The appearance of giant shadows that seemed to move by themselves due to the movement of the cloud layer (this movement is another part of the definition of the Brocken Specter), and which were surrounded by optical glory halos, may have contributed to the reputation the Harz mountains hold as a refuge for witches and evil spirits. In Goethe's Faust, the Brocken is called the Blocksberg and is the site of the Witches' Sabbath on Walpurgis Night.