All phenomena
Bright spots flanking the sun caused by refraction of light through hexagonal ice crystals in the atmosphere
The sun spawning two mirror-image clones -- a triple boss encounter where you have to figure out which sun is the real one!
The science
Horizontally oriented hexagonal plate-shaped ice crystals in cirrostratus clouds refract sunlight at a minimum deviation angle of 22 degrees, creating bright spots on each side of the sun.
How to spot it
Look for bright, rainbow-tinged patches on either side of a low sun when thin cirrus or cirrostratus clouds are present. Hold your arm outstretched and spread your hand -- the distance from thumb to pinky is roughly 22 degrees.
Where
Common in cold climates: Canada, Scandinavia, Russia, the northern US, and Antarctica. Also visible from anywhere with high cirrus clouds.
Best season
Winter months when ice crystal clouds are most prevalent and the sun stays low on the horizon (November-February in the Northern Hemisphere).
Famous encounter
The Battle of Mortimer's Cross (1461) during the Wars of the Roses began with a parhelion display. Edward IV took it as a divine sign and adopted the 'Sun in Splendour' as his emblem.
- ▸Appear as two bright patches exactly 22 degrees on either side of the sun
- ▸Often display a reddish tint on the side closest to the sun
- ▸Most vivid when the sun is near the horizon
- ▸Can sometimes complete a full 22-degree halo ring around the sun