The image above shows a rare lunar halo. Most halos around the sun or moon are common 22-degree halos. They’re caused by ice crystals in the upper air. The ice crystals are typically plate- or column-like hexagonal crystals. But the multiple halo you see in Soumyadeep Mukherjee’s image above is different. It comes from pyramidal ice crystals.
According to sky optics guru Les Cowley, pyramidal crystals tumble more in the air. And so they usually form only rather fuzzy circular halos. Les’ page on these halos, which are sometimes called odd-radius halos, mentions halos of 9-, 18-, 20-, 23-, 24- and 35-degree radius: multiple rings around the moon.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. 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.
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