An extraordinary sight appeared in the Kathmandu sky on Monday morning. On the left side of the sun, a vertical streak of colorful light, resembling a rainbow, was shining brightly. Although many mistook it for a regular rainbow, it was actually a rare optical phenomenon known as a sundog. Remarkably, this phenomenon can appear even in the absence of rain.
According to science, a sundog occurs when tiny hexagonal ice crystals suspended in thin clouds called cirrus or cirrostratus high in the atmosphere refract and reflect sunlight. When the light bends at an angle of about 22 degrees, colorful spots, similar to rainbows appear to the left or right of the sun. In Monday morning’s sky over Kathmandu, the spot was clearly visible on the left side of the sun.
This phenomenon is usually more prominent during sunrise or sunset when the sun is near the horizon. Sometimes, a vertical column of light, known as a light pillar, can also appear along with it. Scientifically, the sundog is also called a parhelion. Although it does not indicate a change in weather, it signals the presence of ice crystals in the upper atmosphere.
The term sundog is believed to have originated from Greek mythology, though its exact origin is uncertain. According to myth, the name refers to the belief that when Zeus, the god of the sky, took his dogs for a walk across the heavens, they appeared as mock suns, accompanying the real sun.
