多洛米蒂山脉安特莫亚湖上的日晕，意大利 Sun halo over Lake Antermoia in the Dolomite Mountains of Italy (© Walter Donega/Getty Images)

多洛米蒂山脉安特莫亚湖上的日晕，意大利 Sun halo over Lake Antermoia in the Dolomite Mountains of Italy (© Walter Donega/Getty Images)

环绕太阳的彩虹 Rainbow around the sun

意大利安特莫亚湖上空的太阳晕

从这里开始，日子只会变长！北半球今天标志着冬天的开始，但冬至也是一年中最短的一天。这里环绕太阳的彩虹，一个太阳光环，位于意大利北部多洛米特山脉的安特摩亚湖上方。当太阳或月亮的光线穿过悬浮在上层大气中的冰晶时，就会形成太阳晕。当太阳光照射到晶体上时，它们就充当了一个棱镜，将光分成光谱中的不同颜色，就像暴雨后彩虹出现的方式一样。

Sun halo over Lake Antermoia, Italy

The days only get longer from here! The Northern Hemisphere marks the beginning of winter today, but the winter solstice is also the shortest day of the year. The rainbow that encircles the sun here, a sun halo, is above Lake Antermoia, in the Dolomite Mountains of northern Italy. Sun halos form when sun or moon light shines through ice crystals suspended in the upper atmosphere. When the light of the sun hits the crystals they serve as a prism, separating the light into individual colors of the spectrum, the same way rainbows occur after a rain shower.