Sundogs–Little Spots of Color in the Sky

August 6, 2012


I love Sundogs, those bright, mysterious spots of color in the sky! They are known by many names, including Mock Suns and Parhelia,  or Phantom Suns, but my favorite is the sun dog. I see them often in New Mexico, which is not surprising. Statistically, they appear 70 days of the year.

Why do they appear so often? Because sundogs are formed when sunlight refracts through the ice crystals of thin layers of high clouds. High clouds would include Cirrus, Cirrostratus, and Cirrocumulus, which are rather common clouds.

A Sundog has a reddish-orange edge facing the sun and a bluish-white tail that shoots out away from the sun. The colors are never crisp, like in a rainbow. They are rather fuzzy, particularly the orange/red section. In my experience, it is sometimes challenging to distinguish the tail from the cloud around it unless the cloud around it is very dark. In fact, they can be seen during any season, but their brightness is determined by the clouds and light around them.

The interesting thing about a Sundog is where it appears. They always appear level to the sun and to the left or right of the sun. I’ve seen them on both sides of the sun. They are said to appear 22 degrees distant from the sun and the same distance above the horizon. According to The Cloud Collector’s Handbook, “the distance from the Sun of both spots of light is equivalent to the outstretched span of a hand held up at arm’s length.”

Ice crystals play an important role in the formation of a Sundog. The ice crystals have to be shaped like hexagonal plates, or by low-lying crystals called Diamond Dust. If the ice crystals in the sky are in random shapes the refracted light will appear as a Sun Halo rather than as a Sun Dog.

Sundogs have quite a history behind them, which adds to their mystery. At times, three Sundogs have appeared in the sky simultaneously.  Cicero, Aristotle, Seneca, and even Shakespeare wrote about Sundogs. When Shakespeare mentions Sundogs he may have referred to an actual historical event, during the War of the Roses, as discussed by Jennifer Young in her article “How a Meteorological Phenomenon Changed English History” on the website Decoded Science.

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