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| Earth on Feb 16, 2013

What is a sun pillar, or light pillar?

Sun pillars, or light pillars, are shafts of light extending from the sun or other bright light source. They’re caused by ice crystals drifting in Earth’s air.

EarthSky Facebook friends occasionally post beautiful photos of sun pillars, or light pillars. They are vertical shafts of light that extend upward (or downward) from a bright light source, such as the sun or other bright light low on the horizon. They can be five to 10 degrees tall and sometimes even higher. They might lengthen or brighten as you gaze at them. They’re beautiful and wondrous. They’re also the source of some UFO reports!

Sun pillar seen by EarthSky Facebook friend Colin Chatfield on November 6, 2012 in Saskatoon, Saskatchewan, Canada. Thank you, Colin. Click here to expand image.

Sun pillar seen by EarthSky Facebook friend Shanna Dennis. Thank you, Shanna. Click here to expand.

Photo credit: EarthSky Facebook friend Kim Smith, taken February 2013. She says “My first ever sun pillar! We don’t often see them here in Walker Creek, Arkansas. I am glad I was out to photograph the sunset today when this occurred.” Thanks Kim!

Sun pillars or light pillars are formed by reflection from hexagonal plate-like ice crystals in Earth’s air. These crystals drift through the atmosphere with a horizontal orientation, gently rocking from side to side as they fall. Diagram via University of Illinois.

Sun pillars or light pillars form when sunlight (or another bright light source) reflects off the surfaces of millions of falling ice crystals associated with thin, high-level clouds, for example, cirrostratus clouds. The ice crystals have roughly horizontal faces. They are falling through Earth’s atmosphere, rocking slightly from side to side.

When is the best time to see a sun pillar or light pillar? You’ll most often see sun pillars when the sun is low in the western sky before sunset, or low in the east just after the breaking of dawn. You might even see a sun pillar when the sun is below the horizon. Light pillars can be seen at any time of night.

View larger. | Wesley Liikane in Severn Bridge, Ontario captured these light pillars on December 23, 2013.   See more photos by Wesley at Cowboy with a Camera on Facebook.

View larger. | Wesley Liikane in Severn Bridge, Ontario captured these light pillars on December 23, 2013. See more photos by Wesley at Cowboy with a Camera on Facebook.

Light pillars caused by work lights on the campus of University of Alaska at Fairbanks. Image via Joseph N. Hall 2005 via Wikimedia Commons.

They’re called sun pillars when the sun helps make them. But this the moon or even streetlights can create this light phenomenon, too, in which case the name light pillar is more appropriate.

These pillars of light often prompt people to report sightings of UFOs. They can sometimes look strange! There are said to be a lot of UFO reports caused by light pillars over Niagara Falls, where the mist from the rush of descending water interacts with the city’s many upward facing spotlights. Light pillars do appear frequently over Niagara Falls, especially during the winter.

As always, the great website Atmospheric Optics is a wonderful place to go and learn more about sun pillars.

Bottom line: Sun pillars, or light pillars, are vertical shafts of light that can sometimes be seen extending upwards or downwards from the sun or other bright light source. They’re caused by light reflection from hexagonal ice crystals drifting in Earth’s atmosphere.