A sun pillar is a vertical shaft of light that appears to extend above (and sometimes below) the sun, most often visible at sunrise or sunset. It’s not a beam of light shooting from the sun itself. Instead, it’s an optical illusion created by sunlight reflecting off millions of tiny ice crystals suspended in the atmosphere.
How Sun Pillars Form
The key ingredient is ice crystals, specifically hexagonal plate-shaped crystals that fall through the air with their flat sides roughly horizontal, gently rocking side to side as they descend. Think of how a leaf flutters as it falls from a tree. That wobbling motion is what makes the whole effect work.
As these flat crystals tilt back and forth, their surfaces act like tiny mirrors. When the sun sits low on the horizon, its light bounces off the undersides of countless crystals at slightly different angles, and the combined reflections create what looks like a tall, glowing column stretching upward from the sun. No single crystal produces the pillar. It’s the collective reflection from an enormous number of crystals spread across a wide area of sky.
This is pure reflection, not refraction. The light isn’t bending through the crystals the way it would to produce a rainbow or halo. Because the light simply bounces off the crystal surfaces, all wavelengths reflect at the same angle, and the pillar takes on the color of the light source rather than splitting into a spectrum.
Why They’re Usually Orange or Red
Sun pillars appear most often when the sun is near the horizon, and that timing directly determines their color. When the sun is low, its light travels through a much thicker layer of atmosphere than it does at midday. Along that extended path, air molecules scatter the shorter blue and violet wavelengths away from your line of sight. The light that makes it through tends to be yellow, orange, or red, with red dominating when the sun sits right on the horizon because red has the longest wavelength of any visible light.
Since a sun pillar is a reflection, it mirrors whatever color the sun appears at that moment. A pillar at early sunset might glow golden yellow, while one at the last sliver of sunset can turn deep red. During the day, when the sun is white, a pillar (if visible at all) would appear white too.
Upper Pillars vs. Lower Pillars
Most sun pillars people notice extend upward from the sun. These upper pillars form when light reflects off the bottom faces of ice crystals overhead. But pillars can also extend downward. A lower pillar forms when light reflects off the top faces of crystals that are below your line of sight.
Lower pillars are harder to spot for a simple reason: you need to be looking down at ice crystals, which usually means you need elevation. Mountain slopes, hilltops, and airplane windows are prime spots. In cold mountain valleys, lower pillars are best seen just after dawn, when the valley is filled with ice fog from a clear, frigid night. Ski slopes are another good opportunity. “Diamond dust,” the sparkling ice crystals that float in clear air on extremely cold days, can produce vivid lower pillars visible even at ground level, especially against a dark background like a shadowed building or snow in shade.
A complete sun pillar extends both above and below the sun, but seeing the full version from the ground requires the sun to be only a few degrees above the horizon and partly shielded by a cloud so the glare doesn’t wash out the lower portion.
When and Where to See One
Sun pillars are most common in cold climates and cold seasons, simply because those conditions produce the most atmospheric ice crystals. High-latitude regions like Alaska, Canada, and Scandinavia see them frequently. But they can appear anywhere that high-altitude cirrus clouds contain plate-shaped ice crystals, which means even temperate regions get them, particularly in winter.
The best time to look is within about 30 minutes of sunrise or sunset, when the sun is low enough for the geometry to work. Calm or light wind conditions help, because strong winds tumble the ice crystals into random orientations instead of letting them fall flat. You want the crystals rocking gently, not spinning chaotically.
Look directly above or below where the sun sits on the horizon. The pillar typically appears as a soft, glowing column, not a sharp beam. It can range from a short stub of light just a few degrees tall to a dramatic streak stretching 20 degrees or more, depending on how many crystals are present and how uniformly they’re oriented.
Light Pillars From Artificial Sources
The same physics that creates a sun pillar works with any bright light source. On very cold nights, streetlights, parking lot lights, and stadium lights can produce vivid vertical columns that stretch upward into the sky. These are commonly called “light pillars,” and they form the same way: ice crystals near the ground reflect the light below them, creating a ghostly column above each light.
Because each light source has its own color, a cityscape on a frigid night can produce dozens of pillars in different hues, red from taillights, white from streetlamps, green from signs. The effect can be so striking that it occasionally gets reported as a UFO sighting. The giveaway is the temperature: light pillars almost always appear on bitterly cold, calm nights when ice crystals fill the lower atmosphere.
Sun Pillars vs. Sundogs and Halos
Sun pillars, sundogs, and halos all involve ice crystals, but they work through different physics. Sundogs and halos are caused by refraction, where light bends as it passes through a crystal. That bending separates white light into its component colors, which is why sundogs and halos often show rainbow-like tints. Sun pillars, by contrast, involve only reflection. The light bounces off crystal surfaces without passing through them, so it stays the same color as the source.
You can sometimes see a sun pillar and sundogs at the same time, since both require plate-shaped ice crystals with a roughly horizontal orientation. If you spot one, it’s worth scanning the sky for the other.