Natural Wonders: Light Pillars

On a cold and clear winter night, you might catch a glimpse of nature’s very own Christmas light show. Light pillars are optical illusions in which thin, vertical beams of light shoot into the sky above or below an artificial or natural light source. These beams are members of the “halo” family and are also called sun pillars, lunar pillars, moon pillars, and luminous pillars. 

Light pillars in North Bay, Ontario. Photo: Timmy Joe Elzinga

 

Halos have been studied since the time of Aristotle. Many cultures have eyed these beautiful displays with suspicion and fear, believing they were signs of an approaching storm — which sometimes they are. Others used it in religious iconography as symbols of purity and sanctity. Rather underwhelmingly, they are simply a trick of the light.

Light pillars vs sundogs

Halos need two key ingredients to be formed: ice crystals and a light source. However, the way in which these two interact makes a big difference. Light pillars are often mistaken for auroras and confused with another optical phenomenon called a sundog (also called a parhelion or mock sun). Sundogs occur when light shines on ice crystals and refract light at exactly 22°, creating a ring around the sun. Light pillars form differently, by reflection rather than refraction.

Sundog on Ellesmere Island. Photo: Jerry Kobalenko

 

Light pillars occur mostly in northern regions but also in deserts at night when temperatures drop to near freezing. Tiny ice crystals in the air drift slowly downward until they’re below or right on the horizon. Each hexagonally shaped crystal becomes a mirror that reflects light from the sun, moon, or street lights just above. The reflection appears as an elongated pillar of light.

The bigger and thicker the ice crystals, the bigger and stronger the light pillar. The colors of the light pillars depend on the color temperature of the light source. The air must be calm because wind disrupts the image. 

How a light pillar works. Photo: Ashley Brauweiler/Shutterstock

 

Meteorologists have linked light pillars and halos in general to the presence of cirrostratus and cirrus clouds. These are very thin, hazy-looking high-altitude clouds made entirely from ice crystals. Most halos associate with these clouds, but sometimes low or even ground-level clouds create the same conditions for pillars to form.

Diamond dust in a light pillar. Photo: w.aoki/Shutterstock

 

Diamond dust

Finally, diamond dust is a low-level mist that appears on frosty winter mornings. Diamond dust forms when temperatures are at least 20°C below freezing and a temperature inversion occurs. This is when colder air near the ground interacts with warmer air above it. The water vapor transforms into ice crystals. When the sun hits the crystals, it looks like the air is full of tiny sparkling diamonds.

Kristine De Abreu is a writer (and occasional photographer) based in sunny Trinidad and Tobago. Since graduating from the University of Leicester with a BA in English and History, she has pursued a full-time writing career, exploring multiple niches before settling on travel and exploration. While studying for an additional diploma in travel journalism with the British College of Journalism, she began writing for ExWeb. Currently, she works at a travel magazine in Trinidad as an editorial assistant and is also ExWeb's Weird Wonder Woman, reporting on the world's natural oddities as well as general stories from the world of exploration. Although she isn't a climber (yet!), she hikes in the bush, has been known to make friends with iguanas and quote the Lord of the Rings trilogy from start to finish.

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Timothy J L Elzinga
5 months ago

I took that picture 🙂