Sun dog

For other uses, see Sun dog (disambiguation).

Very bright Sundogs in Fargo, North Dakota.

Pronounced sun dogs on both sides of a setting sun in New Ulm, Minnesota. Note the halo arcs passing through each sun dog.

An elongated parhelion alongside the sun, unseen at the left

Sun dog in central Iowa, exhibiting rainbow colors

A sun dog or sundog (scientific name parhelion, plural parhelia, for "beside the sun") is a particular type of ice halo. It is a colored patch of light to the left or right of the sun or moon, 22 (or more) degrees distant and at the same distance above the horizon as the sun or moon. It is the most commonly or second most commonly seen of the ice halos. Sundogs can be seen anywhere in the world during any season. In Europe or USA they might be seen 1-2 times a week but not always obviously bright. They are best seen and at their most conspicuous when the sun is low.

Formation and characteristics

A parhelion at the South Pole. The sun is obscured.

Sundogs are formed by plate shaped hexagonal ice crystals in high and cold cirrus clouds or - during very cold weather - by ice crystals called diamond dust drifting in the air at low level.

Sundog forming rays enter a near vertical prism side face of a crystal and exit through a second side face inclined 60-degrees to the first. There is net refraction at each face and the light is dispersed into colors. There is no single angle of deviation through the crystal, which effectively acts as a 60 degree prism, but the minimum angle of deviation is ~22 degrees. This correspond to the distance of the inner edge of the sundog from the sun when the sun is low.

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 further from the sun. However, they always stay at the same altitude 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 theoretically 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 sun dogs.

History

Greece

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.

Cicero

An unusually pronounced sun dog produced by sunlight passing through thin cirrus clouds. The true sun is located outside of the picture to the right.

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.

Wars of the Roses

The prelude to the Battle of Mortimer's Cross is supposed to have involved the appearance of a complete parhelion with three "suns". The Yorkist commander, later Edward IV, convinced his initially frightened troops that it represented the Holy Trinity- Edward's troops won a decisive victory.

Jakob Hutter

Possibly the earliest clear description of a sun dog 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 …

The observation most likely occurred in Auspitz (Hustopeče), Moravia in very late October or very early November of 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. (This quote is also referenced by Fred Schaaf on page 94 of the November 1997 and December 1997 issues of Sky & Telescope.)

Vädersolstavlan

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 still can be seen in the church Storkyrkan in central Stockholm.

Woodcut of 1561 German event

Nuremberg, Germany in 1561

On April 14 1561, the skies over Nuremberg, Germany were filled with a multitude of celestial objects that were observed by many people in the city. The objects were depicted five years later in the 1566 woodcut by Hans Glaser of the "1561 Nuremberg event", that is displayed to the left. Several of the images resemble the types of phenomenon that occur as parhelia or halos.

Shackleton

File:410px-Sun halo optical phenomenon.jpg

A parhelion at the South Pole

In her history Shipwreck at the Bottom of the World: The Extraordinary True Story of Shackleton and the Endurance, telling the story of Endurance's ill-fated polar expedition in 1912, Jennifer Armstrong writes:

… All around them, too, were signs that the Antarctic winter was fast approaching: there were now twelve hours of darkness, and during the daylight hours petrels and terns fled toward the north. Skuas kept up a screeching clamor, and penguins on the move honked and brayed from the ice for miles around. Killer whales cruised the open leads, blowing spouts of icy spray. The tricks of the Antarctic atmosphere brought mock suns and green sunsets, and showers of jewel-coloured ice crystals.

In fiction

A reference to 'parhelia' occurs in the Introduction to Vladimir Nabokov's 1962 novel Pale Fire:

The short (166) Canto One, with all those amusing birds and parhelia, occupies thirteen cards.

        ...and that rare phenomenon
        The iridule--when beautiful and strange,
        In a bright sky above a mountain range
        One opal cloudlet in an oval form
        Reflects the rainbow of a thunderstorm...

In the fifth novel of the Aubrey–Maturin series, Desolation Island, Patrick O'Brian writes:

A visit to the cabin showed him the glass lower still: sickeningly low. And back on the poop he saw that he was by no means the only one to have noticed the mounting sea – an oddly disturbed sea, as if moved by some not very distant force; white water too, and a strange green colour in the curl of the waves and in the water slipping by. He glanced north-west, and there the sun, though shining still, had a halo, with sun-dogs on either side. Ahead, the aurora had gained in strength: streamers of an unearthly splendour.

In her popular historical novel about Richard III of England, The Sunne in Splendour, Sharon Kay Penman writes:

Hastings laughed, too, and shook his head. 'Men do make their luck, Lady Margaret, and never have I seen that better proven than at Mortimer's Cross. For ere the battle, there appeared a most fearsome and strange sight in the sky.' He paused. 'Three suns did we see over us, shining full clear.'

In a footnote it is clarified: "Phenomenon known as a parhelion, generally caused by the formation of ice crystals in the upper air."

Two pages later, again mentioning the English king Edward IV, she adds: "Many, she saw, flaunted streaming sun emblems to denote her son's triumph under the triple suns at Mortimer's Cross."

Shakespeare also appears to mention the phenomenon in his Henry VI, Part 3 when he has Edward say, "Dazzle mine eyes, or do I see three suns?"

Sun dogs appear in the film The Deer Hunter. At the beginning of the film, as the men are leaving work, they see the phenomenon. Robert De Niro's character describes it as an 'old Indian thing' and "A blessing on the hunter sent by the great wolf to his children".

The horror fiction writer Stephen King has a novella called The Sun Dog.

Jane Gardam at the end of her novel Old Filth has the main character, Edward Feathers, see a parhelion from the window of a plane at sunrise on New Years Day:

Later he looked down upon a fat carpet of clouds and saw something he had never seen in his life before. Two suns stood side by side in the sky. A parhelion. A formidable and ancient omen of something or other, he forgot what.".

Sun dogs are referenced in Rush's 1989 song "Chain Lightning" on the album Presto. Neil Peart (lyricist) has been quoted as saying:

"I'm a weather fanatic...I watch the weather...and one night I was watching it and there are two incidents in that song that are synchronicity to one weather report where the weatherman showed a picture of sun dogs...they're a really beautiful natural phenomenon and I love the name, too. Sun dogs just has a great sound to it."

The band Of Montreal used the image in the lyrics to "The Past Is a Grotesque Animal" on the 2007 album Hissing Fauna, Are You the Destroyer?:

I've played the unraveler, the parhelion
But even Apocalypse is fleeting
There's no death, no ugly world

The British neofolk band Death in June put out an EP called "Sun dogs" in 1994.

The minor league hockey team, the Arizona Sundogs, is named after this phenomenon. Their logo features the letter "S" surrounding twin suns.

Jack London has a short story called The Sun Dog Trail.

"Sundog" is the title of a novel by Jim Harrison.

One of Robert Rauschenberg's early experiments in 1962 employing the silk-screen process to reuse previously published images in "Combine Paintings" is titled "Sun Dog".

The poem Die Nebensonnen ("The Parhelia"), by Wilhelm Müller from his 1823-24 cycle Winterreise, was set to music by Franz Schubert: it begins "Drei Sonnen sah ich am Himmel stehn..." ("Three Suns I saw in the sky").

In the 1947 novel Mrs. Mike, Sgt. Mike Flannigan, a Canadian Mountie, explains sun dogs when they are seen by his young Bostonian wife for the first time. Claiming to have observed as many as sixteen of them together in the sky at a single time, he says the Indians believe they are "evil stars trying to kill the sun," but that they are actually caused by atmospheric conditions, and that when they appear "ten to one there's a blizzard by the morning."

Athens, Georgia based jam band Perpetual Groove have back to back songs titled "Perihelion" and "Sun Dog" on their 2003 release Sweet Oblivious Antidote. They are instrumental tracks.

See also

Extremely rare kind of sun dog: the false sunrise

• 120° parhelion
• Anthelion
• Circumhorizontal arc
• False sunrise
• Liljequist parhelion
• Moon dog
• The Miracle of the Sun

External links

• Sundogs - Parhelia, Explanations and Images, Les Cowley's Atmospheric Optics site
• [http://www.atoptics.co.uk/halo/dogim0.htm Sundogs Gallery, Les Cowley's Atmospheric Optics site
• Optical Phenomena - Photos of sun dogs
• Starry Night Photography - Sun Dog, Sun Halo, Moon Halo - Some photos and some text
• Atmospheric Optics - Ice Halos
• Sundog Splendor! video with marvelous close-ups
• Sun dogs, 4 Suns in the Sky Together
• Ice Halos and other atmospheric optics, with free simulation software
• Images by Crayford Manor House Astronomical Society