ODD-RADIUS SUN HALOS: Many sky watchers have witnessed a halo around the sun–a single ring of light that surrounds the solar disk at a radius of 22 degrees. The phenomenon is caused by pencil-shaped ice crystals in cirrus clouds that bend sunlight. On April 26th, Harlan Thomas of Bowness, Alberta, witnessed rare concentric halos:
“I was working in the yard doing spring cleaning when I saw these most unusual halos around the sun,” says Thomas. “I have really never seen multiple halos around the sun before. It was so funny. I was running around on the street looking for the right tree to block the sun, and people were asking what I was looking at. At first they couldn’t see it–then it was Wow what is that!?“
The answer is odd-radius sun halos. They are caused by ice crystals in the shape of pyramids. Sunlight passing through these unusual crystals creates rings with radii of 9, 18, 20, 23, 24 and 35 degrees. At least 2 or 3 of those are present in Thomas’s photo.