Pillars

Last updated on September 16, 2023

Pillars: A Spectacular Atmospheric Optics Phenomenon

Have you ever witnessed a breathtaking sight where narrow columns of light seemingly beam directly up and sometimes downwards from the sun? These mesmerizing optical phenomena are known as pillars. Typically visible near sunset or sunrise, pillars can reach heights of 5 to 10 degrees, and occasionally even higher. While they may appear as vertical rays, they are actually the collective glints of millions of ice crystals.

When it comes to colors, pillars are truly a sight to behold. They take on hues that reflect the sun and surrounding clouds, ranging from brilliant white to various shades of yellow, red, or purple. Depending on the locations of the cloud crystals, pillars can even manifest as several vertically strung patches of light. As the light interacts with the ice crystals in the atmosphere, it creates a stunning display that captivates observers.

If you find yourself lucky enough to witness a pillar, pay close attention after sunset. You might notice that they gradually lengthen and intensify in brightness. As the sun moves below the horizon, these pillars can be seen creeping northwards (or southwards in the Southern Hemisphere) for up to 30 to 60 minutes after it has set at ground level. This prolonged display provides an extended opportunity to marvel at the beauty of these atmospheric wonders.

While the phenomenon of pillars is awe-inspiring, it is important to understand their scientific explanation. Pillars are formed when light interacts with hexagonal ice crystals suspended in the air. These crystals act as tiny prisms, refracting and reflecting sunlight in specific directions. When the crystals align horizontally, they create the illusion of a vertical column of light extending from the sun.

The size and shape of the ice crystals play a significant role in determining the appearance of pillars. Larger crystals tend to produce more pronounced and elongated pillars, while smaller crystals may result in shorter and less defined columns. Additionally, the orientation of the crystals can influence the direction and shape of the pillars. As the crystals drift through the atmosphere, they continuously change their positions, leading to dynamic and ever-changing displays of light.

To fully appreciate the phenomenon of pillars, it is essential to observe them in the right conditions. Look for pillars near sunset or sunrise when the angle of the sun is low on the horizon. Clear skies with a moderate amount of high-altitude clouds are ideal, as these clouds often contain the ice crystals necessary for pillar formation. Patience is key, as pillars may not always be visible or may appear faint. However, when conditions align perfectly, the spectacle that unfolds in the sky is truly worth the wait.

While sun pillars are the most commonly observed type of pillar, similar phenomena can also occur with other light sources, such as streetlights or even the moon. These artificial light pillars can add a touch of enchantment to urban landscapes during cold winter nights. By understanding the science behind these optical marvels, we can better appreciate the beauty and wonder that nature bestows upon us.

In conclusion, pillars are a captivating atmospheric optics phenomenon that transforms the sky into a canvas of radiant light. From their narrow columns extending from the sun to their ever-changing colors and shapes, pillars never fail to astound and inspire. So, keep your eyes peeled during those magical moments near sunset or sunrise, and you may just be fortunate enough to witness the enchanting dance of pillars in the sky.

Sunset Pillar at Sutherland's Lake, Nova Scotia, 30th December'02 imaged by Shaun Lowe (more of his images) A lower sun pillar was visible earlier. ©2002 Shaun Lowe, shown with permission.

Look for sun pillars near to sunset or sunrise.

They are narrow columns of light apparently beaming directly up and sometimes downwards from the sun. They can be 5 -10º tall and occasionally even higher.

Pillars are not actually vertical rays, they are instead the collective glints of millions of ice crystals.

Pillars take on the colours of the sun and clouds, they can appear white and at other times shades of yellow, red or purple.

Sometimes they appear as several vertically strung patches of light depending on the locations of the cloud crystals.

Pillars often lengthen and brighten after sunset. Watch them creeping northwards (southwards in the Southern Hemisphere), following the sun's movement below the horizon, for up to 30 to 60 minutes after it has set at ground level.

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Reference Atmospheric Optics

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