This article was accepted into the corpus but its outbound wikilinks were never NER-processed — typical at the deepest BFS hop or when the run's entity cap was reached. No expansion funnel to show.
| Ring Around the Moon | |
|---|---|
| Name | Ring Around the Moon |
| Phenomenon | Halo |
| Causes | Ice crystals in cirrostratus clouds |
| Occurrence | Worldwide |
Ring Around the Moon is an atmospheric halo phenomenon produced when Moonlight is refracted and reflected by hexagonal ice crystals in high-altitude cirrostratus clouds, often forming a luminous circle at approximately 22 degrees from the lunar disk. Observers across Antarctica, Greenland, Sahara Desert, Himalayas, and urban centers such as New York City and London have reported this feature, which has been documented by scientists affiliated with institutions including NASA, European Space Agency, National Oceanic and Atmospheric Administration, and university observatories like Harvard University and University of Cambridge.
A ring appears when near-parallel Moonrays interact with randomly oriented hexagonal ice prisms in cirrostratus cloud layers, yielding a halo centered on the lunar position and commonly measuring about 22 degrees in radius. The effect arises from refraction and internal reflection processes first quantified by optical physicists at laboratories such as Royal Society and described in classic texts from researchers at Max Planck Society, Smithsonian Institution, and observatories at Mount Wilson Observatory and Greenwich Observatory.
The physics of the halo invokes Snell's law and dispersion analyzed by scientists at University of Oxford, Massachusetts Institute of Technology, and California Institute of Technology, with computational modeling adopted by teams at Jet Propulsion Laboratory and European Southern Observatory. Polarization, color separation, and intensity variations are governed by crystal habit distributions studied by researchers at Scripps Institution of Oceanography, University of Colorado Boulder, and Institut Pierre-Simon Laplace, while radiative transfer and scattering formulations are used by groups at Princeton University and Imperial College London.
Variants include the common 22-degree halo, uncommon 46-degree halos reported by observers in Chile and Iceland, tangent arcs recorded near Mount Etna and Mount Fuji, supralateral and infralateral arcs documented by expeditions to Antarctica and Svalbard, and phenomena such as parhelia and paraselene observed in polar campaigns led by teams from British Antarctic Survey and Norwegian Polar Institute. Subtle forms like concentric halos and diffuse coronae have been photographed by amateurs in Tokyo, Sydney, and Toronto and analyzed by citizen science projects associated with Zooniverse.
Historically, halos around the Moon have been noted in chronicles from Babylon, Ancient Rome, and Imperial China, appearing in annals archived at British Library, Library of Congress, and National Palace Museum. Folklore tying halos to weather prediction circulated in treatises collected by Royal Society and Académie des Sciences, while poets such as William Shakespeare and philosophers like Immanuel Kant referenced luminous rings in works preserved at Bodleian Library and Bibliothèque nationale de France. In modern times the phenomenon features in photography competitions hosted by National Geographic Society, Royal Photographic Society, and media from outlets including BBC and The New York Times.
Notable scientific observations include measurements by expeditions led by James Clark Ross in the 19th century, spectrophotometric studies during the International Geophysical Year coordinated by World Meteorological Organization and International Council for Science, and high-altitude balloon campaigns conducted by Columbia University and Pennsylvania State University. Artists and naturalists such as John James Audubon and Caspar David Friedrich depicted moon halos in works now in collections at Metropolitan Museum of Art and Louvre Museum. Contemporary notable events include halo displays photographed during lunar eclipses observed by teams at McDonald Observatory and Kitt Peak National Observatory.
Quantitative study employs CCD photometry, polarimetry, and spectroscopy using instruments at Palomar Observatory, Keck Observatory, and spaceborne sensors from NOAA and ESA missions, with data processed using codes developed at Los Alamos National Laboratory and National Center for Atmospheric Research. Field campaigns combine ground-based lidar from AERONET sites, radiosonde launches coordinated by World Meteorological Organization, and satellite remote sensing from MODIS and CALIPSO to retrieve ice crystal size, shape, and concentration. Peer-reviewed analyses appear in journals published by American Geophysical Union, Royal Meteorological Society, and European Geosciences Union.
Category:Atmospheric optical phenomena