A parhelion, more commonly called a sun dog, is a bright spot of light that appears to one or both sides of the sun. On the right day you can see two of them, one either side, as if the sky had three suns. It is one of the most striking atmospheric phenomena you can see with the naked eye, and it has inspired several of our designs.

This article explains what a parhelion is, how it forms, when you are most likely to see one, and how it found its way into the Parhela collection.

What is a parhelion?

A parhelion is an optical effect caused by sunlight passing through ice crystals in the atmosphere. It appears as a patch of bright light, sometimes white and sometimes softly coloured, roughly 22 degrees to the left or right of the sun. The plural is parhelia.

The word comes from Greek and means "beside the sun", a precise description of what you see. In English the phenomenon is better known as a sun dog, a name whose origin is uncertain but which has been in use for centuries.

How do sun dogs form?

Sun dogs form when sunlight passes through flat, six-sided ice crystals drifting in high, thin clouds such as cirrus or cirrostratus. As the crystals fall, they tend to settle horizontally, like leaves dropping through still air.

When sunlight enters one side of a crystal and leaves through another, it bends, or refracts, by about 22 degrees. Millions of crystals aligned in the same way send that bent light towards your eyes from the same angle, creating a bright spot beside the sun.

Why are sun dogs sometimes coloured?

Different wavelengths of light bend by slightly different amounts as they pass through ice. Red light bends the least, so the side of a sun dog closest to the sun often looks reddish, fading to yellow and blue further out. When the crystals are less well aligned, the colours blur and the sun dog looks whiter.

Halos and parhelic circles

Sun dogs often appear alongside a 22-degree halo, a faint ring of light circling the sun. On rare occasions, a horizontal band of white light called a parhelic circle runs through the sun and both sun dogs, linking them across the sky.

When and where can you see a sun dog?

Sun dogs can appear anywhere in the world, in any season, whenever the right ice crystals are present. A few conditions make them more likely:

• A low sun. Sun dogs are brightest and easiest to spot when the sun is near the horizon, early in the morning or late in the afternoon.
• Thin, high cloud. A veil of cirrus or cirrostratus provides the ice crystals.
• Cold air. They are especially common in very cold regions, but they also appear in temperate skies, including over London.

To look for one, stand with the sun in front of you and shield it with your hand. Then look roughly a hand-span with outstretched fingers to the left and right. Never look directly at the sun.

Sun dogs in history and culture

People have recorded sun dogs for thousands of years, often reading them as signs or omens. Accounts of "three suns" appear in chronicles from many periods, and the phenomenon has long fascinated painters, writers and scientists. Today it is studied as part of atmospheric optics, alongside rainbows, glories and halos.

How the parhelion inspires our designs

The poetry of a parhelion, light, cold and the perfect symmetry of nature, runs through several of our pieces.

Story of a Parhelion Pants

The Story of a Parhelion Pants are bi-colour bottoms with intricate embroidery positioned on both the front and the back. The embroidery illustrates the ethereal conditions that give rise to the phenomenon, and the pants are meticulously crafted in London. Find them alongside our other bottoms in joggers and trackpants.

The Parhelion Silk Shirt

The Parhelion Silk Shirt, cut from 100% satin silk, carries a meticulously embroidered patch on the back that reimagines the parhelion as a surreal cosmic tableau: two moons flanking a central sun. Discover it with the rest of our silk shirts and shorts.

The Parhelion Cap

The Parhelion Cap is made by a partner hat maker in Indonesia from scrap fabrics collected from landfills and manufacturers, with a six-panel construction and an adjustable strap. You will find it in our accessories.

Light and sky across the collection

The sky is a recurring source for us. Our Celestial Collection uses an Italian wool blend with yarns needle punched in random celestial patterns, so that every piece is unique. Read how it was developed in a year in the making: inside the Celestial Collection, or learn more about the technique in our guide to needle punch fabric.

In short

A parhelion, or sun dog, is a bright patch of light about 22 degrees beside the sun, created when sunlight refracts through flat, six-sided ice crystals in high, thin clouds. It is easiest to see when the sun is low and a veil of cirrus covers the sky. The phenomenon inspires several Parhela pieces, from the embroidered Story of a Parhelion Pants to the Parhelion Silk Shirt. Explore them in the full collection, and read more about our values in our manifesto.