Rare light pillars dazzle Barrie-area residents, here’s what to know about the phenomenon

Barrie's extreme cold conditions were expressed in a light show called 'light pillars' that appear as numerous white pillars of white light against a black sky.

Residents across the Barrie, Ont., area were treated to a rare and extraordinary sight early Thursday morning as columns of light stretched across the sky just before sunrise.

The phenomenon, known as light pillars, occurs under very specific atmospheric conditions, says an astronomical expert, and is not commonly seen in southern Ontario.

Many residents captured the glow over Barrie around 5:30 a.m. Thursday and shared their awe on social media.

What are light pillars?

According to Jenna Hinds, executive director of the Royal Astronomical Society of Canada, light pillars form when tiny ice crystals develop in the atmosphere and fall horizontally.

Light from objects close to the horizon (like streetlights or the sun as it is rising) shines upward and reflects off the horizontal ice crystals.

“They’re a bunch of tiny mirrors, and shines back to your eyes on the surface of the earth in the form of a pillar,” Hinds explains.

What conditions cause this to happen?

Light pillars require a mix of cold temperatures, calm air, and humidity.

“Wind disturbs the horizontal fall of the ice crystals, and if the crystals aren’t aligned horizontally, the light is scattered and does not form pillars, so conditions must be calm,” Hinds says. “You need some sort of humidity so that there’s moisture available to freeze into ice crystals.”

Because southern Ontario doesn’t often experience this mix of conditions, light pillars are considered an uncommon sight in the region.

Family of atmospheric phenomena

Hinds says light pillars are in the same family of atmospheric phenomena as halos, which are phenomena produced when light meets ice crystals in the atmosphere.

“If you’ve ever seen a sort of circle of light around the sun or moon, that’s a similar phenomenon called a halo,” shares Hinds. “Another similar phenomenon is called a sun dog, which forms at specific points along that halo, and it often splits into a rainbow.”