What is a parhelion?
A parhelion, also nicknamed “false sun” or “sun dog”, is an optical phenomenon that occurs when sunlight passes through ice crystals suspended in the atmosphere. These crystals, often found in cirrus or cirrostratus clouds, act like natural prisms, refracting and reflecting light. This interaction gives rise to bright points to the left and right of the sun, often accompanied by a circular halo.
Parhelia typically appear 22 degrees on either side of the sun, forming a sort of bright trio. Although they vary in intensity, they can sometimes be bright enough to be mistaken for a second sun. This phenomenon is therefore purely optical and does not reflect any celestial anomaly.
Why did this phenomenon occur in Valmorel?
As you can see, the Valmorel resort, perched at an altitude of 1,400 meters in the Alps, offers a favorable setting for observing this type of spectacle. Parhelia occur primarily in cold regions where suspended ice crystals are abundant. In winter, low temperatures and often clear mountain skies favor the formation of cirrus-type clouds.
In addition, the intense light of the raking sun, characteristic of winter days, accentuates the refraction and dispersion of light. These conditions were clearly met on the day these stunning images were captured by the station.
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