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Parhelic circle and 2 halos over Alberta, Canada

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August 3, 2021

The sun to one side, with a 22-degree halo around it, and a 2nd arc, the parhelic circle, extending from the halo. — View at EarthSky Community Photos. | Parhelic circle and 2 solar halos captured August 1, 2021 by Gord Hurlburt. He caught the image in Kananaskis Country, a recreation area to the west of Calgary, Alberta, Canada, in the foothills and front ranges of the Canadian Rockies.

Parhelic circle and 2 halos

Gord Hurlburt captured this remarkable image on August 1, 2021, while hiking down from Burstall – Piggy Plus Col in Kananaskis, Alberta, Canada. You can see the sun on the far right of the image. Around it are two halos. The inner halo is known as a 22-degree halo. The outer is known as a circumscribed halo. Angling out from those two sun-circling halos is another arc. It’s called a parhelic circle. All of these phenomena – the 22-degree halo, the circumscribed halo, the parhelic arc – are caused by ice crystals in the air.

Check out this image from Les Cowley’s Atmospheric Optics website. It shows the same configuration of halos and circles over Tibet that you saw, Gord, over Alberta, Canada.

Plus Les Cowley has a illustration (below) that shows the parhelic circle and explains more.

Diagram of sun with halos and enlarged, labeled ice crystals. — In this schematic, the sun is surrounded by a 22-degree halo and flanked by parhelia, aka sundogs. Notice the parhelic circle cutting through the sundogs and extending beyond them. Notice that it cuts through the sun. Sky optics guru Les Cowley wrote that the parhelic circle: “… sometimes encircles the whole sky at the same altitude as the sun.” Image via Cowley’s Atmospheric Optics.

By the way, Gord, in your posting, you mentioned parhelia, aka sundogs. We’re not seeing the sundogs in this image, but, sure enough, the 2nd arc looks as if it’s cutting across the 22-degree halo (and circumscribed halo) just at the spot where a sundog might be.

Bottom line: A photo from an EarthSky community member showing portions of a 22-degree halo, circumscribed halo and parhelic circle.

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August 3, 2021

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Deborah Byrd

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Deborah Byrd (asteroid 3505 Byrd) helps edit EarthSky.org and is a frequent host of EarthSky videos. Deborah created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Prior to that, she had worked for the University of Texas McDonald Observatory since 1976, and created and produced their Star Date radio series. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named in her honor in 1990, a Public Service Award from the National Science Board in 2003, and the Education Prize from the American Astronomical Society in 2020. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.