When sundogs appear, they resemble a "halo" around the Sun. There is a distinct parallel arch of light stretching around the Sun with two larger lights on both the right and left side of the Sun that look like two additional suns. The term sundog comes from the Greek word parhelion, which means "beside the sun." Sundogs are an atmospherical phenomenon that have been written about and recorded for centuries.
Sundogs can appear around the Sun, but also appear around the Moon. In colder climates, ice crystals in the air, which appear like sparkly dust, can also create sundogs. Sundogs can occur during any season and can be seen worldwide. They are always easier to spot when the sun is low on the horizon and the halo, with its accompanying twin suns, is just above the horizon line.
Sundogs are formed when the ice crystals in a cirrus cloud line up in such a way that the light shining through them creates a rainbow. Ice crystals inside the cirrus clouds create the sundog because of the way the light reflects and bends or refracts when passing through the crystals.
Sundogs can appear to be white or rainbow-colored. The closer to the Sun, the redder the sundog will appear, with the other colors appearing further away from the Sun. Unlike a rainbow, however, the colors are not distinct and will overlap and fade making it hard to identify them in the spectrum. The variance in color depends on how the light reflects and refracts or bends when it hits the ice crystals.
Throughout history there have been documented occurrences of sundogs. From Aristotle to Aratus in Ancient Greece to Cicero in Rome, sundogs have been cited in literature, poetry and philosophical works. Sundogs have also been captured in paintings and other works of art over the centuries, proving that they are not just a modern atmospheric phenomena. Jack London even wrote a short story called "The Sun-Dog Trail" in 1905.
- Wonder Quest with April Holladay: What is a Sundog and what makes it happen?
- WFMZ-TV 69 News: What is a "Sun Dog"
- "Rainbows, Mirages, and Sundogs;" Roy A. Gallant; Aug. 1987
- Alaska Science Forum: "Sun Dogs and Light Shafts;" Kolf Jayaweera; Apr. 1976
- Photo Credit Jupiterimages/Photos.com/Getty Images
- "The Sun-Dog Trail, and Other Stories;" Jack London; 1951
- "A First Course in Atmospheric Thermodynamics;" Grant W. Petty; May 2008
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