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Astro Bob: Crystal blue confusion

How snowflakes in a clear, blue sky created a confounding halo.

Snow crystal oval halo Jan 15 2022
A peculiar halo arcs partway around the sun around 9 a.m. on Saturday, Jan. 15. Its cause made me scratch my head.
Contributed / Bob King
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Saturday morning (Jan. 15) I stepped outside in the cold sunshine and admired the snowy fluff that had accumulated on the deck. Temperatures were in the single digits overnight and the air absolutely still, allowing multitudes of the feathery dendrites to gently lodge between each other's spines. When I positioned my eye just right, I could catch the specular (mirror-like) flash of sunlight from individual flakes. The effect was intense, with single snowflakes blazing like miniature suns from the soft heaps.

Snowflake in sunshine Jan 15 2022
A snowflake that reflects sunlight like a tiny mirror stands out against the masses of flakes surrounding it.
Contributed / Bob King

Snow, swept up by a gentle breeze, occasionally fell from the cloudless sky. Then I noticed something weird. A small, oval halo ringed the sun. I've seen halos before but not one like this. The most common type is a big circle called the 22° halo because it has a radius of 22° — about two fists. Ice crystals in high-elevation cirrostratus clouds bend or refract sunlight at a 22° angle to create this relatively common yet very beautiful sight.

Halo and sun pillar pane
(Left) Ice crystals in high clouds create familiar 22° halos around the sun and moon. The "star" to the left of the moon in this photo is Jupiter. Sunlight reflecting from six-sided, plate-shaped ice crystals floating in the air make sun pillars (right).
Contributed / Bob King

There are also ice pillars , which appear near sunrise and sunset. A pillar looks like a beam or column of light standing over the low sun. It's caused by the collective glints of countless plate-shaped ice crystals hovering in the air with their flat sides parallel to the ground. The icy plates mimic tiny mirrors like the specular snowflake pictured in the photo.

Snow crystal oval halo Jan 15 2022
Neither changing my position or snow blowing across the scene altered the oval's appearance.<br/>
Contributed / Bob King

But this was different. First off, it appeared in a clear, blue sky. Second, it was shaped like a hoop, not a circle. I saw it on three occasions over 15 minutes for about a minute each time. So I snapped on a telephoto lens, racked the focus in and out and discovered the source, which you've probably already guessed by now. It was the selfsame, airy-light snowflakes I'd been photographing up close but plucked and lofted by the breeze. Somehow, I don't know how, they reflected or refracted sunlight to create the odd bow, one I'd never seen before.

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Snow crystal oval halo Jan 15 2022 blowing snow detail
Throughout the halo's appearance, the dust-like snow drifted through the air. I used a telephoto lens during a "good blow" to better show the flakes.
Contributed / Bob King

There's a small possibility it's the enlarged shadow of the tree projected onto airborne snow drifting in the foreground. But when I moved around, the oval remained the same shape and at the same height. Nor did freshly-blown snow from the trees in the foreground alter its appearance.

I'm curious if you've ever seen something similar and might be able to help me out. That's one reason I wanted to share this with you. The second is to tell you that you never know when nature will change your plans. I sat down more than an hour late to breakfast, hungrier and happier than ever.

Read more from Astro Bob
The forecast held true, with a very dark moon during totality. The likely culprit? Volcanic dust.

"Astro" Bob King is a freelance writer for the Duluth News Tribune.

Related Topics: SCIENCE AND NATURE
"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune.
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