Nature stories

The physics of a parhelion is similar to that of rainbows, but with two important differences:

Firstly, rainbows are caused by water droplets in the atmosphere acting like prisms, splitting the sunlight into its constituent colours, whereas parhelia are caused by atmospheric ice-crystals behaving in a similar way.

Secondly, rainbows appear in the sky opposite the Sun, but parhelia appear about 22° degrees either side of the Sun.

Depending on the nature of the ice crystals, parhelia can range from diffuse smudges to extremely bright, well-defined Sun-like images.

Parhelion from Martin Humphries' garden

They can also vary from white to highly coloured, and often have a white 'tail' pointing away from the Sun.

I took this photograph of one from my garden in Kidderminster at 7:04pm on 23 May 2007, which shows a bright, highly coloured parhelion, complete with tail, immediately above the central tree.

It remained in the sky for 10 to 15 minutes after I first saw it - the Sun is just out of frame to the left of the picture.

UFOs and battles

Parhelia are not particularly rare phenomena (one every three days at any given site on average), but the reason most are not seen is that people simply don't look at the sky!

However, very bright ones, that are seen by many people, are rare, which may account for the effect that three 'Suns' appearing in the sky had on the superstitious opposite sides of the Battle of Mortimer’s Cross – terrifying one side and inspiring the other!

Parhelia have another claim to fame. In the 1950's, the American Government took the possibility of alien spacecraft very seriously, and scrambled their fighter planes whenever anything unusual was seen in the skies.

To the best of my knowledge, not a single 'flying saucer' was intercepted, and it turned out that the most common cause of scrambling the aircraft were sightings of sundogs!