On 17 May 1986 Dutch people saw a bright circle around the sun. Coming three weeks after the Chernobyl disaster, this unusual phenomenon caused great consternation. The Royal Netherlands Meteorological Institute was flooded with calls asking if the halo was linked to radioactive particles in the air. At the time the idea was dismissed, but now it turns out that Dutch observers may have been right.
Since Babylonian times halos have provoked fascination and superstition; King Edward IV of England even used them to help him win a battle during the War of the Roses. Today we know they are caused by high level ice crystals acting like chandelier crystals, scattering light. Sometimes halos can presage a storm, when sunlight is scattered by ice crystals in high level cirrus clouds on the storm’s front edge. Writing in the journal Weather, Mila Zinkova describes halos she saw during the Californian wildfires in 2017. She concludes that the smoke from the fires encouraged formation of high level ice crystals, enhancing the chances of halos being seen. Similarly, Zinkova suggests that the radionuclides ejected by the Chernobyl disaster in 1986 might have served as nuclei for the ice crystals that caused halo sightings over the Netherlands.
