An astronomer in Nottingham has revealed why people across the city and beyond may have seen a 'halo' around the moon this week.
Professor of astronomy at the University of Nottingham, Michael Merrifield, managed to capture the "beautiful" phenomenon on the evening of March 23.
Despite the rings around the moon having a perfectly normal explanation, the sight left many baffled.
Xara Lou, who lives in Arnold, told Nottinghamshire Live: "Well, after 2020, I honestly thought 'what now?'
"But apparently it is a thing. It is a moon halo and they are more common than rainbows. I cannot believe I have never seen one before if that is the case."
Pictures were shared on social media to the amazement of those who missed the spectacle themselves.
Professor Merrifield said the phenomenon is commonly known as the "22-degree winter halo".
He said: "In the deeper image, taken lying on my back in the road, you can see that the inner edge is reddish while the outer edge is bluer.
"Although known to be caused by hexagonal ice crystals refracting the moonlight, the exact geometry is still a matter of speculation."
The optical phenomenon is created when millions of ice crystals refract the light from the sun, which bounces off the moon, creating a halo which has an apparent radius of around 22-degrees around the sun or moon depending on the time of day.
Because no light is refracted at angles less than 22-degrees, the sky within the halo (closer to the sun or moon) appears much darker.
This gives the effect of a 'halo' around the object.
According to current science, the exact shape of the ice crystals and the 22-degree orientation remain up for debate.
NASA says: "Each ice crystal acts like a miniature lens.
"Because most of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22-degrees, which corresponds to the radius of the moon halo.
“A similar sun halo may be visible during the day. Exactly how ice-crystals form in clouds remains under investigation."
The phenomenon is indeed more common that rainbows, up to 100 days per year, but people generally miss the sight as they never tend to look up.
