The upper patch of dull color in this photo taken last week from Duluth is a circumzenithal arc touching part of a larger 46-degree halo. The inner concentric rings around the sun are a rare halo phenomenon caused by pyramid-shaped ice crystals in high cirrostratus clouds. Photo: Bob King
Last Wednesday as the sun dropped in the west, it was surrounded by a remarkable series of halos I’d never before seen. Most common halos are caused by light refracted or bent by microscopic, six-sided ice crystals that look like cut up pencils. Light enters one side of the crystal and is bent at a 22-degree angle as it exits the other side. All the millions of crystals together create a ring around the sun with a radius of 22 degrees.
This is the cropped and enhanced version of the halo pictured above. The sun is ringed by 9, 18 and 22 degree halos, a couple of which show color along their edges. Because pyramid ice crystals have many different faces at a variety of angles to one another, they can create multiple odd-dimension halos. Photo: Bob King
This halo was different. I first noticed a colorful patch, called a circumzenithal arc, well above the main halo. You’ll see in the photo that light continues on either side of the arc to form part of the larger, rarer 46-degree halo. What really caught my eye however were the several nested halos within the space between the sun and the normal 22-degree halo.
After a search through books and online sources, I discovered that these odd, concentric halos were caused by pyramidal ice crystals. In the contrast-enhanced picture you can count at least three of them near the sun.
What amazes me is that you can see hundreds of halos in your lifetime and still not see them all. The constant interplay of light and ice has surprises in store for both daytime and nighttime skywatchers. For more on this unusual phenomenon, you can visit this website.
I’m not the only one that’s been busy with their camera. We’ve also received some really nice photos from our readers in the past week. Here they are for you to enjoy. Thank you Lyle and Andrew for sending them.
The fair city of Duluth reflects on a calm Lake Superior last Thursday night. Photo credit: Lyle Anderson
The International Space Station cuts a path of light through the sky from Duluth’s Park Point Sunday morning. The little wiggle at the far left end of the trail was caused by camera movement, possibly the wind. At upper right, you can see the W of Cassiopeia. Photo credit: Lyle Anderson
The photo of lightning bugs last week inspired photographer Andrew Kirk of Bishop, Calif. to send this picture of colorful water trails. "Drops of water flung from a rushing mountain stream catch sunlight as they spin and distort. A single drop may rotate and reflect numerous times during its flight and even refract mini-rainbows back to the camera," Kirk writes. Photo credit: Andrew Kirk