Sun dog

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For other uses, see Sun dog (disambiguation).
Very bright sundogs in Fargo, North Dakota. Note the halo arcs passing through each sundog.
Left-hand sun dog at Stonehenge
Right-hand sun dog in Salem, Massachusetts, Oct 27, 2012. Also visible are a Parry arc, an upper tangent arc, a 22° halo and part of the parhelic circle.
Sun dogs in Hesse, August 12, 2012

Sun dogs (or sundogs), mock suns[1] or phantom suns,[2] scientific name parhelia (singular parhelion), are an atmospheric phenomenon that consists of a pair of bright spots on either side on the sun, often co-occurring with a luminous ring known as a 22° halo.[3]

Sun dogs are a member of a large family of halos, created by light interacting with ice crystals in the atmosphere. Sun dogs typically appear as two subtly-colored patches of light to the left and right of the sun, approximately 22° distant and at the same elevation above the horizon as the sun. They can be seen anywhere in the world during any season, but they are not always obvious or bright. Sun dogs are best seen and are most conspicuous when the sun is low.

A 22° halo seen in summer, India --- Kolkata

Formation and characteristics[edit]

Sundogs are commonly made by the refraction of light from plate-shaped hexagonal ice crystals in high and cold cirrus clouds or, during very cold weather, these ice crystals drift in the air at low levels, in which case they are called diamond dust. The crystals act as prisms, bending the light rays passing through them with a minimum deflection of 22°. If the crystals are randomly oriented, a complete ring around the sun is seen — a halo. But often, as the crystals sink through the air, they become vertically aligned, so sunlight is refracted horizontally — in this case, sundogs are seen.

As the sun rises higher, the rays passing through the crystals are increasingly skewed from the horizontal plane. Their angle of deviation increases, and the sundogs move farther from the sun.[4] However, they always stay at the same elevation as the sun.

Sundogs are red-colored at the side nearest the sun. Farther out the colors grade through oranges to blue. However, the colors overlap considerably and so are muted, never pure or saturated. The colors of the sundog finally merge into the white of the parhelic circle (if the latter is visible).

It is possible to predict the forms of sundogs as would be seen on other planets and moons. Mars might have sundogs formed by both water-ice and CO2-ice. On the giant gas planets — Jupiter, Saturn, Uranus and Neptune — other crystals form the clouds of ammonia, methane, and other substances that can produce halos with four or more sundogs.[5]

Etymology[edit]

The exact etymology of sun dog largely remains a mystery. The Oxford English Dictionary states it as being "of obscure origin".[6]

In Abram Palmer's 1882 book Folk-etymology: A Dictionary of Verbal Corruptions Or Words Perverted in Form Or Meaning, by False Derivation Or Mistaken Analogy, sun-dogs are defined:

The phenomena [sic] of false suns which sometimes attend or dog the true when seen through the mist (parhelions). In Norfolk a sun-dog is a light spot near the sun, and water-dogs are the light watery clouds; dog here is no doubt the same word as dag, dew or mist as "a little dag of rain" (Philolog. Soc. Trans. 1855, p. 80). Cf. Icel. dogg, Dan. and Swed. dug = Eng. "dew."[7]

Alternatively, Jonas Persson suggested that out of Norse mythology and archaic names in the Scandinavian languages, constellations of two wolves hunting the sun and the moon, one after and one before, may be a possible origin for the term.[8]

Parhelion (plural parhelia) comes from Greek παρήλιον (parēlion), meaning "beside the sun"; from παρά (para), meaning "beside", and ἥλιος (helios), meaning "sun".[9]


History[edit]

Sun dog phenomenon depicted in the Nuremberg Chronicle

Greece[edit]

Aristotle (Meteorology III.2, 372a14) notes that "two mock suns rose with the sun and followed it all through the day until sunset." He says that "mock suns" are always to the side, never above or below, most commonly at sunrise or sunset, more rarely in the middle of the day.

The poet Aratus (Phaenomena 880–891) mentions parhelia as part of his catalogue of Weather Signs; according to him, they can indicate rain, wind, or an approaching storm.

Artemidorus in his Oneirocritica ('On the Interpretation of Dreams') included the mock suns amongst a list of celestial deities.[10]

Rome[edit]

A passage in Cicero's On the Republic (54–51 BC) is one of many by Greek and Roman authors who refer to sun dogs and similar phenomena:

Be it so, said Tubero; and since you invite me to discussion, and present the opportunity, let us first examine, before any one else arrives, what can be the nature of the parhelion, or double sun, which was mentioned in the senate. Those that affirm they witnessed this prodigy are neither few nor unworthy of credit, so that there is more reason for investigation than incredulity.[11]

Seneca makes an incidental reference to sun dogs in the first book of his Naturales Quaestiones.[12]

The 2nd century Roman writer and philosopher Apuleius in his Apologia XV says "What is the cause of the prismatic colours of the rainbow, or of the appearance in heaven of two rival images of the sun, with sundry other phenomena treated in a monumental volume by Archimedes of Syracuse."

Wars of the Roses[edit]

The prelude to the Battle of Mortimer's Cross in Herefordshire, England in 1461 is supposed to have involved the appearance of a complete parhelion with three "suns". The Yorkist commander, later Edward IV of England, convinced his initially frightened troops that it represented the three sons of the Duke of York, and Edward's troops won a decisive victory. The event was dramatized by William Shakespeare in King Henry VI, Part 3,[13] and by Sharon Kay Penman in The Sunne In Splendour.

Jakob Hutter[edit]

Possibly the earliest clear description of a sundog is by Jacob Hutter, who wrote in his Brotherly Faithfulness: Epistles from a Time of Persecution:

My beloved children, I want to tell you that on the day after the departure of our brothers Kuntz and Michel, on a Friday, we saw three suns in the sky for a good long time, about an hour, as well as two rainbows. These had their backs turned toward each other, almost touching in the middle, and their ends pointed away from each other. And this I, Jakob, saw with my own eyes, and many brothers and sisters saw it with me. After a while the two suns and rainbows disappeared, and only the one sun remained. Even though the other two suns were not as bright as the one, they were clearly visible. I feel this was no small miracle…[14]

The observation most likely occurred in Auspitz (Hustopeče), Moravia on October 31, 1533. The original was written in German and is from a letter originally sent in November 1533 from Auspitz in Moravia to the Adige Valley in Tyrol. The Kuntz Maurer and Michel Schuster mentioned in the letter left Hutter on the Thursday after the feast day of Simon and Jude, which is October 28. The Thursday after was October 30.[15]

Vädersolstavlan[edit]

The so-called "Sun Dog Painting" (Vädersolstavlan) depicting Stockholm in 1535 and the celestial phenomenon at the time interpreted as an ominous presage

While mostly known and often quoted for being the oldest colour 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 sun dog. For two hours in the morning of April 20, 1535, the skies over the city were filled with white circles and arcs crossing the sky, while additional suns appeared around the sun. The phenomenon quickly resulted in rumours of an omen of God's forthcoming revenge on King Gustav Vasa (1496–1560) for having introduced Protestantism during the 1520s and for being heavy-handed with his enemies allied with the Danish king.

Hoping to end speculations, the Chancellor and Lutheran scholar Olaus Petri (1493–1552) ordered a painting to be produced documenting the event. When confronted with the painting, the king, however, interpreted it as a conspiracy - the real sun of course being himself threatened by competing fake suns, one being Olaus Petri and the other the clergyman and scholar Laurentius Andreae (1470–1552), both thus accused of treachery, but eventually escaping capital punishment. The original painting is lost, but a copy from the 1630s survives and can still be seen in the church Storkyrkan in central Stockholm.[16]

Influence on Descartes in 1629[edit]

A set of powerful parhelia in Rome in the Summer of 1629 caused René Descartes to interrupt his metaphysical studies and led to his work of natural philosophy called "The World".[17]

See also[edit]

References[edit]

  1. ^ The American Heritage Dictionary of the English Language http://education.yahoo.com/reference/dictionary/entry/mock%20sun
  2. ^ Phantom Sun- 3 suns over China spotted
  3. ^ The American Heritage Dictionary of the English Language, 2004
  4. ^ Cowley, L. "Effect of solar altitude". Atmospheric Optics. Retrieved 2007-04-15. 
  5. ^ Cowley, L. "Other Worlds". Atmospheric Optics. Retrieved 2007-04-15. 
  6. ^ "Sundog". Oxford English Dictionary. Retrieved 2013-12-30. 
  7. ^ Palmer, Abram Smythe (1882). Folk-etymology: A Dictionary of Verbal Corruptions Or Words Perverted in Form Or Meaning, by False Derivation Or Mistaken Analogy. G. Bell and Sons. Retrieved 2013-12-30. 
  8. ^ Persson, Jonas. "Norse Constellations". Digitalis Education Solutions, Inc. Retrieved 2013-12-30. 
  9. ^ "Parhelion". Oxford English Dictionary. Retrieved 2013-12-30. 
  10. ^ p.125 Artemidorus – The Interpretation Of Dreams Oneirocritica by Artemidorus Translation and Commentary by Robert J. White c.1975 1990 Oriingal Books, Inc. 2nd Edition Published in the U.S. ISBN 0-944558-03-8
  11. ^ Cicero; CD Yonge (trans.) (1877). "On the Commonwealth, Book 1". Project Gutenberg. pp. (260), 367, (369). 
  12. ^ Seneca, Ricerche sulla Natura, P. Parroni editor, Mondadori, 2010
  13. ^ The Mortimer’s Cross Parhelion: How a Meteorological Phenomenon Changed English History
  14. ^ Jakob Hutter (1979). Brotherly Faithfulness: Epistles from a Time of Persecution. Rifton, NY: Plough Publishing. pp. 20–1. ISBN 0-87486-191-8. 
  15. ^ Schaaf, Fred (November, December 1997), Sky & Telescope, p. 94  Check date values in: |date= (help)
  16. ^ Pererik Åberg (2003-07-10). "Vädersolstavlan". Stockholm: Sveriges Television. Retrieved 2007-01-28. 
  17. ^ René Descartes - Metaphysical turn, Stanford Encyclopaedia of Philosophy

External links[edit]