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sun pillar[′sən ‚pil·ər]
an optical phenomenon in the atmosphere. Sun pillars are streaks of white or, sometimes, slightly reddened light extending above and below the sun. They are observed primarily in winter when the weather is cold and are best seen at sunrise and sunset. Sun pillars occur when horizontally arranged flat hexagonal ice crystals (plates) are present in the atmosphere. The pillars are a result of the reflection of the sun’s rays from the bases of the crystals, which are slowly falling toward the earth’s surface. Light pillars are also sometimes seen above and below the moon.