Ice halo around the moon seen in the UK

Pictured is the moon halo over the, Isle of Wight. The moon halo is formed by a high-altitude ice crystal cloud that gathers around the moon

Last night many observers in the UK reported seeing an odd halo of light around the moon.

The remarkable phenomenon was captured in stunning images, showing the moon surrounded by a bright ring of light.

The spectacle is caused by ice crystals in the atmosphere, specifically when thin cirrus or cirrostratus clouds are present at an altitude of about 20,000 feet (6,100 metres).

During cold weather these clouds can contain millions of hexagonal ice crystals, and as light from the moon - which is just reflected sunlight - passes through the atmosphere, it refracts in a particular way within the crystals.

Specifically, the light refracts at angles no smaller than 22° - sometimes leading the phenomenon to be called a 22° halo - which results in a ring around 44 times larger than the moon itself.

Different colours of light are bent at different angles, resulting in the inner edge of the halo being slightly red, and the outer edge having a slightly bluer tint.

The light refracts at angles no smaller than 22° in the ice crystals (illustrated) - sometimes leading the phenomenon to be called a 22° halo - which results in a ring around 44 times larger than the moon itself

The reason that it forms as a ring is because of the angle of refraction. The only light that reaches your location is that which is located at the right distance away from the moon to form a ring. Here, a vapour trail from a plane is seen cutting through the halo above Herefordshire

The effect is not exclusive to the moon, however. It can also occur around the sun, for the same reasons described above.

On some occasions the halos are accompanied by sundogs - bright spots either side of the moon or sun as the crystals sink through the air, causing the light to be vertically aligned.

'Ice halos are atmospheric phenomena that can occur around the sun or the moon, when tiny crystals of ice in the atmosphere refract and reflect light, creating a halo around the solar or lunar source,' Ben Biggs, Editor for magazine, told MailOnline.

'Visually, they can range from the one we could see last night in parts of the UK, which was a cool and slightly creepy perfect circle around the moon, to a bright and ethereal display featuring multiple arcs and 'sundogs' (also known as parhelia), which appear as bright spots at the corners of the halo when the sun is near the horizon.'

'Even the more ordinary halos are fairly uncommon in the UK but in particularly bright and bitter conditions, such as in the US, absolutely spectacular ice halo displays can appear.'

Ice halos were once said to be a sign that a storm was approaching, as cirrus or cirrostratus clouds often come before a large storm front.

However, the clouds can also occur without a large storm approaching, so their use as an accurate weather prediction tool is not entirely accurate.

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