In extremely cold weather, a striking optical phenomenon can sometimes be observed, where it appears as though there are two suns in the sky. This second "sun" is known as the "ghost" sun, also scientifically referred to as the anthelion. Unlike celestial bodies, the anthelion is not an actual object but a type of mirage, resulting from specific atmospheric conditions.
The formation of this phenomenon begins with the presence of tiny ice crystals suspended in the atmosphere. These ice crystals, usually found in cirrus clouds at high altitudes, are the central players in creating the anthelion. As sunlight passes through these crystals, it gets bent or refracted in a specific manner due to the unique shape and orientation of the crystals. This bending of light rays is what generates the illusion of a second sun.
The process is somewhat similar to how rainbows are formed, with each ice crystal acting like a miniature prism. However, what makes the anthelion distinct is the way the light reflects and refracts inside the hexagonal ice crystals typically found in cold weather conditions. The light rays enter through one face of the crystal and exit through another, creating the appearance of the sun's mirror image on the opposite side of the sky from the actual sun.
This ethereal duplicate can appear quite vivid and is most often visible when the sun is low on the horizon, either early in the morning or late in the afternoon. The visual intensity of the anthelion can vary depending on the density and uniformity of the ice crystals, as well as the angle of the sunlight. Under ideal conditions, the anthelion can be a compelling sight, inspiring both awe and a variety of mythical stories and interpretations through the ages.
While the phenomenon is purely optical and scientific, its infrequent and startling appearance continues to capture the imaginations of those lucky enough to observe it. Thus, the anthelion not only enriches our understanding of atmospheric science but also adds a touch of mystical beauty to the cold, sometimes bleak winter landscape.
