Did YOU see a 'halo' surrounding the moon last night?
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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).
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
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.
Here the moon halo is spotted over London. The bright 'star' to the left of the moon in the image is Jupiter, which is making its closest approach to Earth until 2019 at the moment
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
This photo, taken in Wales, shows the large halo; its radius is roughly the size of an outstretched hand at arms length
Some people online took to Twitter to express their amazement at seeing the moon ring
The phenomenon occurs when the sky is full of thin cirrus or cirrostratus clouds, seen as a thin wisp on the left in an image taken by Jason Hedges, 41 at his home in West Wittering in Sussex. Different colours of light are bent at different amounts, so the inner edge of the halo is slightly red, and the outer edge is slightly more blue, seen on the right above St Catherine's lighthouse, Isle of Wight
The effect was visible to observers across the UK including the Isle of Wight and in Herefordshire
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 All About Space 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.'
Other users on Twitter were not so lucky, with some bemoaning the cloudy conditions that made the effect not visible
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.
The images also show the gas giant planet Jupiter near the moon. The planet is due to make its closest approach to Earth until 2019 this Friday 6 February, so it is particularly bright and visible in the night sky at the moment.
Known as opposition, the event will see Jupiter come within 404 million miles (650 million kilometers) of Earth.
SUNDOGS: SEEING THREE SUNS
Shown are sundogs apppearing either side of the sun in Fargo, North Dakota
The sight of three suns in the sky is enough to make most of us rub our eyes in disbelief, but centuries ago, the strange sight was seen as a bad omen. The unusual spectacle is called a parhelion or a sundog.
It is the result of a natural phenomenon in which sunlight passes though snow crystals in a particular way when they are suspended in the air.
Sundogs are created when sunlight is refracted by large, hexagonal ice crystals, such as those in snowflakes.
They typically appear as two coloured patches of light either side of the sun and though rare, can in theory be seen anywhere in the world in any season.
They are created by the refraction of light passing through flat, hexagonal ice crystals in high, cold clouds.
The crystals act like prisms so that as light passes through them, it is bent by exactly 22 degrees before reaching viewers' eyes to make the illusion.
If the crystals are more randomly located in clouds, a complete ring around the sun is visible, called a halo.
But if the crystals sink through the air, they become arranged in vertical lines, so that the sunlight is refracted horizontally, to make sundogs, as seen in these images.
If the phenomenon is seen as the sun is rising, the sundogs gradually move further away from the sun, but always stay at the same elevation, so the three 'orbs' appear to be the same distance from the horizon.
They are reddest in colour when they are near to the sun and fade to yellow, orange and then blue as they move away. The colours of sundogs merge into a white halo in some instances.
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