What is a Sun Pillar?

Sun pillars are vertical beams of light reflected off ice crystals as the sun nears or sinks below the horizon

The sun is getting ready to set or has just dropped below the horizon, but much like a movie premiere, a spotlight appears, shooting straight out the top of the sun.

There is no movie, but it is essentially lights, camera, action!

The beams, known as sun pillars, are formed when the sunlight passes through a layer of flat, six-sided ice crystals typically found in high-altitude cirrus clouds.

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"So it's kind of like a dinner plate," said Michael Kavulich with the National Center for Atmospheric Research. "And if there are very calm conditions, they'll settle in a horizontal orientation, and they can essentially act like mirrors."

The sunlight will then bounce off each ice crystal, creating a majestic display.

"Imagine thousands of little mirrors in between you and the sun, and they're all facing horizontally at different heights," Kavulich said. "So just a tiny little image of the sun is being reflected off of each one of these tiny mirrors, and it ends up forming this horizontal column that we call a pillar."

Kavulich says calmer conditions found in the lower altitudes are crucial to getting the crystals appropriately aligned.

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"You don't tend to get these (pillars) from the high-altitude crystals because up in the high atmosphere, it's very rare to get very calm conditions," Kavulich said. "There's almost always wind, and it's fairly turbulent up there. Whereas when you get much colder conditions near the ground, you tend to have these (plate) ice crystals that are much closer to the ground. And then when you get the nice calm conditions, these ice crystals will fall."

City lights can make their own pillars too

While the sun is the most common source of pillars, a bright moon can sometimes make a pillar, too. 

But if it’s a rather cold night, dramatic pillars of lights can shine above where manufactured lights sit below.

"When you see light pillars at night, that's due to actually lights at ground level reflecting off of these horizontal kinds of (ice) mirror crystals," Kavulich said.

It can happen higher in the sky when thin, icy clouds pass over city lights, like this display in Hansville, Washington.

But ice pillars can be an even more dramatic sight stretching from the ground in or near the Arctic and other places where temperatures reach well below freezing and the ice crystals are near the surface.

According to the Atmospheric Optics site, pillars from artificial light can stretch taller than natural light pillars because the "rays from the lights are not parallel and plate crystals with small tilts can still reflect (the light) downwards."

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The crystals have to be about halfway between you and the light source for the pillar to form. The Optics site says if it’s a freezing night and ice crystals surround you, even lights nearby like streetlights can give off pillars.