What is a sun pillar, or light pillar?

What is a sun pillar, or light pillar?

By Deborah Byrd in
FAQS | EARTH on Mar 22, 2016
http://facebook.com/earthsky

http://earthsky.org/earth/what-is-a-sun-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. For example, there was a beautiful one seen from the U.S. West Coast on March 20, 2016 … a beautiful prelude to the first full night of spring. Sun pillars 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_Shanna_Dennis
Sun pillar photo by Shanna Dennis

Photo by Lyle Evans in Highland, California.

The U.S. West Coast got an amazing sun pillar on the first evening of spring. Photo by Lyle Evans in Highland, California.

March 20, 2016, from the U.S. West Coast. This one is from Chris Levitan Photography CA

Another shot of the beautiful sun pillar seen on March 20, 2016, from the U.S. West Coast. This one is from Chris Levitan Photography.

plate-like_ice_crystalssunpillar100_big

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.

Wesley Liikane in Severn Bridge, Ontario captured these light pillars on December 23, 2013

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. https://www.facebook.com/CowboyWithACamera

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.

sun_pillar_Colin_Chatfield_sunset_11-6-2012_Saskatoon_SAskatchean

Sun pillar seen by EarthSky Facebook friend Colin Chatfield on November 6, 2012 in Saskatoon, Saskatchewan, Canada.

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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.”

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.

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http://www.weatheronline.co.uk/reports/wxfacts/Sun-pillar.htm

Sun pillars are seen best within a few minutes of sunrise or sunset. Initially the have about the same colour and width as the sun, but sun pillars will gradually change their colour from orange-white to red-orange. Sun pillars generally fade 20 to 60 minutes after sunset. Under favourable conditions, e.g. icy fog, sun pillars might stretch out up to 30° above the sun, while light streaks of 5° to 10° are most common.

On rare occasions, regarded with awe in more superstitious times, it may occur with part of the parhelic cycle to give the appearance of a cross centred on the Sun. The sun pillar is comparable with the light course, the setting sun produces on a water surface.

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