On February 27, 2018, Star Cammy on Facebook posted this this photo. Immediately, her friends began buzzing about whether the photo showed random cloud iridescence or a fragment of a circular corona around the sun. In fact, the cloud iridescence and coronas are related, both caused by the diffraction of light by tiny water droplets (sometimes small ice crystals) in clouds.
Matthew Chin, a friend of Cammy’s in Hong Kong and also a friend of EarthSky’s, solved the mystery by writing to sky optics guru Les Cowley about Cammy’s photo. Les, who runs the amazing website Atmospheric Optics, called it a distorted corona around the sun, produced by a non-uniformity in the size of the water droplets that are creating the rainbow-like colors.
Les’ response is below. You can also check out Matthew’s blog about this photo (if you can read Chinese).
Bottom line: A photo of a distorted corona around the sun, captured over Hong Kong in February 2018.
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.