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Science Behind The Beaming Pillars Of Light

Anuj Mudaliar Feb 8, 2019
Ice crystals come in innumerable shapes and sizes, which is why when light from the Sun, Moon, or artificial light passes through a concentration of the crystals, optical illusions/apparitions such as halos, Sun dogs, and pillars are formed.

Where are Light Pillars Found?

Typically seen in the polar regions, vertical columns of light appear in places having lower altitudes and frigid temperatures. Most light pillars consist of approximately 10 - 100 million rays of light.

Requirements to View Light Pillars

The location and appearance of any light pillar depends on 5 factors: The orientation and type of the floating ice crystals, the height of the crystals in the atmosphere, the height of the light source, and the distance of the crystals from the observer.
Also, crystals that are far away from the observer need to have greater tilts, as compared to crystals that are closer, in order for the pillars to be visible.

Light Pillar or Camera Flare?

Although the light pillars appear similar to lens flares in photographs, the only difference being that they can be viewed by the naked eye, while lens flares cannot.

Direction of Light Pillars

When the source of light is close to the ground, the light pillars appear above the ice crystals. But if the Sun or Moon is the source, the pillars can extend below and/or above the crystals.

Why Light Pillars Are So Rare

Light pillars are rare because the plate-shaped ice crystals are usually found only in high altitude clouds, but when such clouds float close to the ground, their facets reflect light back downwards, creating the pillars.

Optical Illusions

When ice crystals are close to the observer and illuminated by artificial lights, the pillars that are formed are quite broad. When the crystals are pushed around by the wind, these pillars vanish and reappear, giving the appearance of a shimmering aurora.

Artificial Light Pillars

Why do Artificial Light Pillars Have Different Colors?

The different colors correspond to the source of the light. Mercury vapor lights produce bluish/red pillars. Sodium lights create yellow/red pillars.

UFO Sighting?

When the floating ice crystals get clumped together in layers of an ice fog, rather than spreading out evenly, light from artificial sources create bizarre broken light pillars in the air, which often spark UFO rumors. If the ice crystals are in separate layers, multiple light pillars can form at different heights, giving them a very psychedelic appearance.

Interesting Light Pillar Trivia

In extremely cold conditions and still air, light pillars can even be caused from the light emitting from the headlights of a car.

Unique Light Pillar Shapes

In rare cases, the ice crystals may be long and columnar in shape (15 - 20 micrometers across, and between -5 to -25°C), rather than the usual flat hexagonal shapes. This can cause the light pillars to gain a trumpet shape, by flaring towards the ends.

Light Pillar Trivia

Unlike other night-sky phenomena, the appearance of light pillars improves, the closer you are to urban areas.

Sizes In Light Pillars

Artificial light pillars can be larger than natural ones, going up to 90 degrees, as the beams from man-made sources are not parallel, and even slightly tilted ice crystals are able turn this light into pillars, from an appropriate distance and angle.
On the other hand, Sun and Moon pillars are visible only when the crystals are tilted at a large angle.

Natural Light Pillars

Sun Pillars

Most light pillars are Sun pillars, formed when sunlight reflects off millions of ice crystals in very cold air (between 0 to -20° C).
These pillars can stretch very high, and can acquire the reds, yellows, and purples of the Sun and the clouds near them. In rarer cases, moonlight and artificial light can also form light pillars.

Characteristics of Sun Pillars

Sun pillars can be 5 - 10 degrees tall, and on rare occasions much more higher.
They are known to lengthen/brighten for around 30 minutes after the Sun has gone below the horizon, and depending on the position of the crystals, the pillars may even appear as multiple vertical strips of light instead of just one.

Hunting for Light Pillars

Sun and Moon pillars are usually seen only when the Sun/Moon are visible close to the horizon. The best time to see a Sun pillar is in the west just before sunset or in the east when the Sun begins to rise.
Artificial light pillars can be seen at anytime of the night. Great views can be seen from hills/mountains or an airplane.

Spotting Downward Sun Pillars

Sun pillars which extend below the Sun are much more difficult to see, than those above the Sun. The best chance of seeing them is after dawn, when the air is filled with an ice fog, following a clear and cold night.

Unique Atmospheric Phenomenon

In very rare cases, some ice crystals, form Sun pillars along with Sun dogs, and halos. This happens because of the two-way rotation of the crystals in the air. The sunlight reflects of the end faces of the crystal, when in a horizontal position, producing the pillar.

Rare Light Pillar Sightings

Sun and moon pillars do not necessarily occur only in the cold seasons. This is because even in warm climates, clouds at an high altitude might contain ice crystals. However, such sightings are very rare.

Hunting Lunar Pillars

A lunar pillar can occur during almost all phases of the moon, provided that the atmosphere is icy, the Moon is bright, and the sky is dark.

Planetary Light Pillars

In exceedingly rare cases, light pillars can also be formed by planets such as Venus. To view such pillars, one has to look at the planet when it is close to a clear horizon, after sunset. Also, the air should have a thin layer of cirrus clouds. These light pillars are best viewed with low-power binoculars.