Hexagonal plate- and column-shaped ice crystals cause the phenomenon. For two hours in the morning of 20 April 1535, the skies over the city were filled with white circles and arcs crossing the sky, while additional suns (i.e., sun dogs) appeared around the Sun.Ī light pillar, or sun pillar, appears as a vertical pillar or column of light rising from the Sun near sunset or sunrise, though it can appear below the Sun, particularly if the observer is at a high elevation or altitude. While mostly known and often quoted for being the oldest color depiction of the city of Stockholm, Vädersolstavlan ( Swedish "The Sundog Painting", literally "The Weather Sun Painting") is arguably also one of the oldest known depictions of a halo display, including a pair of sun dogs. Vädersolstavlan The so-called "Sun Dog Painting" ( Vädersolstavlan) depicting Stockholm in 1535 and the celestial phenomenon at the time interpreted as an ominous presage 1794).Ĭhinese observers had recorded these for centuries, the first reference being a section of the "Official History of the Chin Dynasty" ( Chin Shu) in 637, on the "Ten Haloes", giving technical terms for 26 solar halo phenomena. 1630), Johannes Hevelius in Danzig (1661), and Tobias Lowitz in St Petersburg ( c. While Aristotle had mentioned halos and parhelia, in antiquity, the first European descriptions of complex displays were those of Christoph Scheiner in Rome ( c. Other common types of optical phenomena involving water droplets rather than ice crystals include the glory and rainbow. They often do indicate that rain will fall within the next 24 hours, since the cirrostratus clouds that cause them can signify an approaching frontal system. The crystals behave like prisms and mirrors, refracting and reflecting light between their faces, sending shafts of light in particular directions.Ītmospheric optical phenomena like halos were used as part of weather lore, which was an empirical means of weather forecasting before meteorology was developed. Light is reflected and refracted by the ice crystals and may split into colors because of dispersion. The particular shape and orientation of the crystals are responsible for the type of halo observed. The ice crystals responsible for halos are typically suspended in cirrus or cirrostratus clouds in the upper troposphere (5–10 km (3.1–6.2 mi)), but in cold weather they can also float near the ground, in which case they are referred to as diamond dust. Among the best known halo types are the circular halo (properly called the 22° halo), light pillars, and sun dogs, but many others occur some are fairly common while others are extremely rare. Many of these appear near the Sun or Moon, but others occur elsewhere or even in the opposite part of the sky. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky.
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