寒冬道路上空的四重月晕

2022年1月2日

Quadruple Lunar Halo Over Winter Road
Image Credit & Copyright: Dani Caxete

Explanation: Sometimes falling ice crystals make the atmosphere into a giant lens causing arcs and halos to appear around the Sun or Moon. One Saturday night in 2012 was just such a time near Madrid, Spain, where a winter sky displayed not only a bright Moon but four rare lunar halos. The brightest object, near the top of the featured image, is the Moon. Light from the Moon refracts through tumbling hexagonal ice crystals into a somewhat rare 22-degree halo seen surrounding the Moon. Elongating the 22-degree arc horizontally is a more rare circumscribed halo caused by column ice crystals. Even more rare, some moonlight refracts through more distant tumbling ice crystals to form a (third) rainbow-like arc 46 degrees from the Moon and appearing here just above a picturesque winter landscape. Furthermore, part of a whole 46-degree circular halo is also visible, so that an extremely rare — especially for the Moon — quadruple halo was captured. Far in the background is a famous winter skyscape that includes Sirius, the belt of Orion, and Betelgeuse — visible between the inner and outer arcs. Halos and arcs typically last for minutes to hours, so if you do see one there should be time to invite family, friends or neighbors to share your unusual lensed vista of the sky.

Tomorrow’s picture: comet tailscape

寒冬道路上空的四重月晕
影像提供与版权: Dani Caxete

说明: 有时候，飘落的冰晶让大气成为巨型透镜，造就了太阳或月亮周围的光弧与光晕。在2012年的某个星期六夜晚，于西班牙马德里附近拍下的冬天星空里，不但拍到明月，更记录了罕见的四重月晕即可为见证。在这幅主题影像顶缘附近的最明亮天体是月亮。其月华受到飘落的六角形冰晶之折射，产生月亮周围有点罕见的22度月晕。让22度月晕在水平方向有点外扩的，是稍更罕见、由柱状冰晶所产生的外晕。而部分月光受到外围较远的冰晶折射，产生美丽冬季地景上方，像彩虹的第三重、更罕见之46度下虹弧。此外，还可看见部分的46度月晕；于是这幅影像，记录了对月亮而言，极端罕见的四重月晕。在远方的背景星空里，有出现在内与外层月弧之间，冬季星空中著名的天狼星、猎人腰带三星、及参宿四。月晕和月弧通常可持续数分钟到数小时之久。所以，当你见到这类的大气透镜景观时，请务必与家人、好友、和邻居分享。 （释注：22-degree halo 22度晕；circumscribed halo 外晕；infralateral arc 下虹弧； 46-degree halo 46度晕）

明日的图片: comet tailscape