EarthSky Facebook friends have posted some beautiful photos recently of sun pillars, sometimes called light pillars. They are vertical shafts of light that extend upward (or downward) from a bright light source, such as the sun 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 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? You’ll most often see one 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.
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 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.