What is a sundog? Are they just another rainbow?
Sundogs are bright spots of light seen on both sides of the Sun. They are also called halos or parhelia. The best time to see sundogs is in the late afternoon, when the Sun is close to the horizon and can be blocked by trees or buildings. Winter seems to be the best season, because the atmosphere tends to be dry and cold, but sundogs are visible throughout the year and around the world when conditions are right. The two bright spots are 22-23 degrees from the Sun, about the distance covered by your outstretched hand held at arms’ length. A line though the sundogs and Sun is parallel to the horizon. Sundogs are a type of ice crystal halo. Scientists had to understand the size, shape, and motion of ice crystals in the Earth’s atmosphere to understand how halos are produced. Sundogs are caused by sunlight passing through flat, 6-sided ice crystals high in the troposphere. The crystals fall through the atmosphere like leaves, flat side more or less down and slowly rocking back and forth. B
