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Encyclopedia > Halo (optical phenomenon)
It has been suggested that Moon dog be merged into this article or section. (Discuss)
It has been suggested that Icebow be merged into this article or section. (Discuss)
For other uses, see Halo (disambiguation).
Halo around the sun at the South Pole (NOAA)
Enlarge
Halo around the sun at the South Pole (NOAA)
Icebow over the Kluane Range viewed from the Alaska Highway (J. Hall)
Icebow over the Kluane Range viewed from the Alaska Highway (J. Hall)
Ice-bow around the sun at temperate latitude. Contrast enhanced for clarity. There is also a brighter nearly white diffraction disk or Airy disk nearer the sun, with red on the outside.
Ice-bow around the sun at temperate latitude. Contrast enhanced for clarity. There is also a brighter nearly white diffraction disk or Airy disk nearer the sun, with red on the outside.

A halo (Greek: ἅλως; also known as a nimbus or Gloriole) is a ring of light that surrounds an object. Image File history File links Please see the file description page for further information. ... A moon dog is a brightening in the clouds caused by the refraction of moonlight in high-atmosphere cirrus clouds. ... Image File history File links Please see the file description page for further information. ... Halo/icebow with sun dogs visible to the left and right (NOAA) An icebow, also known as a halo, is phenomenon similar to a rainbow except that it is formed by the diffraction of sunlight through cloud suspended ice crystals as opposed to raindrops or other liquid water suspended in... Look up halo on Wiktionary, the free dictionary. ... Image File history File links Download high-resolution version (1220x1784, 1191 KB) Description: A magnificent halo South Pole Station is visible in the background Source: http://www. ... Image File history File links Download high-resolution version (1220x1784, 1191 KB) Description: A magnificent halo South Pole Station is visible in the background Source: http://www. ... Image File history File links AlcanSunbow. ... Image File history File links AlcanSunbow. ... Map of Alaska Highway (in red) The Alaska Highway, also the Alaskan Highway, Alaska-Canadian Highway, and the Alcan Highway, runs from Dawson Creek, British Columbia to Fairbanks, Alaska, via Whitehorse, Yukon. ... Joseph N. Hall (born January 8, 1966) is an American author, software developer and programming consultant. ... Image File history File links Download high resolution version (1136x852, 202 KB) Summary Digital camera picture taken in Palo Alto, CA. Contrast enhanced to make the image clearer. ... Image File history File links Download high resolution version (1136x852, 202 KB) Summary Digital camera picture taken in Palo Alto, CA. Contrast enhanced to make the image clearer. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Categories: Optics | Science stubs ...


Halos, also known as icebows, are also optical phenomena that appear near or around the Sun or Moon, and sometimes near other strong light sources such as street lights. There are many types of optical halos, but they are mostly caused by ice crystals in cold cirrus clouds located high (5–10 km, or 3–6 miles) in the upper troposphere. The particular shape and orientation of the crystals is responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split up into colors because of dispersion, similarly to the rainbow. Halo/icebow with sun dogs visible to the left and right (NOAA) An icebow, also known as a halo, is phenomenon similar to a rainbow except that it is formed by the diffraction of sunlight through cloud suspended ice crystals as opposed to raindrops or other liquid water suspended in... An optical phenomenon is any observable event which results from the interaction of light and matter. ... The Sun is the star of our solar system. ... Bulk composition of the Moons mantle and crust estimated, weight percent Oxygen 42. ... Icicles A natural ice block in Iceland Ice is the solid form of water. ... A cirrus cloud is a type of cloud composed of ice crystals and characterized by thin, wisplike strands, often accompanied by tufts. ... View of Earths troposphere from an airplane. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength [citation needed]. The elementary particle that defines light is the photon. ... Spheres reflecting the floor and each other. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ... Icicles A natural ice block in Iceland Ice is the solid form of water. ... Color is an important part of the visual arts. ... Dispersion of a light beam in a prism. ... Full featured rainbow in Wrangell-St. ...

Halo around moon
Halo around moon

Sometimes in very cold weather optical halos are formed by crystals close to ground level, called diamond dust. The crystals behave like jewels, refracting and reflecting sunlight between their faces, sending shafts of light in particular directions. Image File history File links Download high resolution version (1600x1600, 54 KB) Halo around moon. ... Image File history File links Download high resolution version (1600x1600, 54 KB) Halo around moon. ...


Atmospheric phenomena such as halos were used as an empirical means of weather forecasting before meteorology was developed. Layers of Atmosphere (NOAA) Air redirects here. ... Empirical is an adjective often used in conjunction with science, both the natural and social sciences, which means an observation or experiment based upon experience that is capable of being verified or disproved. ... Modern weather predictions aid in timely evacuations and potentially save lives and property damage Weather map of Europe, 10 December 1887 Weather forecasting is the application of current technology and science to predict the state of the atmosphere for a future time and a given location. ... Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ...

Contents

Sundogs

Main article: Sun dog
Complex system of lunar halos (J. Hall)
Complex system of lunar halos (J. Hall)
Halo with sun dogs visible to the left and right (NOAA)
Halo with sun dogs visible to the left and right (NOAA)

Sun dogs, also known as parhelia (single parhelion), appear as near-horizontal colored spots or bars on both sides of the sun, at nearly a 22 degree angle. Sun dogs are uncommon and typically appear only when a low sun shines through loose cirrus clouds, e.g., in a milky-white winter afternoon sky. The orientation of the ice crystals involved in this process is important. The crystals are hexagonal cylinders, and they have to be oriented vertically. An unusually pronounced sundog produced by sunlight passing through thin cirrus clouds. ... Image File history File links LunarIceHalos. ... Image File history File links LunarIceHalos. ... Joseph N. Hall (born January 8, 1966) is an American author, software developer and programming consultant. ... Image File history File links Sundog_. ... Image File history File links Sundog_. ... A cirrus cloud is a type of cloud composed of ice crystals and characterized by thin, wisplike strands, often accompanied by tufts. ... A right circular cylinder An elliptic cylinder In mathematics, a cylinder is a quadric, i. ...


When the sun dog phenomenon is seen around the Moon rather than the Sun, it is called a moon dog, or by the proper name paraselene.


Light pillar

Sun pillar near Harpers Ferry, West Virginia (NOAA)
Sun pillar near Harpers Ferry, West Virginia (NOAA)
Main article: Light pillar

A 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. Hexagonal plate- and column-shaped ice crystals cause the phenomenon. Plate crystals generally cause pillars only when the sun is within 6 degrees of the horizon, or below it; column crystals can cause a pillar when the sun is as high as 20 degrees above the horizon. The crystals tend to orient themselves near-horizontally as they fall or float through the air, and the width and visibility of a sun pillar depends on crystal alignment. Image of a Sun Pillar from the NOAA Photo Library, part of the National Weather Service Weather Wonders collection. ... Image of a Sun Pillar from the NOAA Photo Library, part of the National Weather Service Weather Wonders collection. ... Pillars from uncovered work lights above University of Alaska Fairbanks (J. Hall) A light pillar is a visual phenomenon created by the reflection of light from ice crystals with parallel planar surfaces. ...


Light pillars can also form around the moon, and around street lights or other bright lights. Pillars forming from ground-based light sources may appear much taller than those associated with the sun or moon. Since the observer is generally closer to the light source, crystal orientation matters less in the formation of these pillars.


See also

The corona is the luminous plasma atmosphere of the Sun extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. ... Full featured rainbow in Wrangell-St. ... NASA photo Glory with aircraft shadow in the center. ... Heiligenschein (holy light) is the name for an optical effect which creates a bright spot around the shadow of a persons head when this person is looking at it. ...

External links

Wikimedia Commons has media related to:
Halo
  • Halo explanations and image galleries at Atmospheric Optics
  • Astronomy Picture of the Day, November 7, 2001
  • Light Pillars
  • Sun pillar, taken at Iona beach May 4, 2005
  • Southern Hemisphere Halo and other atmospheric phenomena
  • Halo photo on EnchanteCeiling.com
  • Catalog with Photos of Types of Halos

 
 

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