Although it may seem to be a lens flare or other digital effect, today’s Astronomy Picture of the Day is in fact a natural phenomenon called a Moon Halo.
Caused by light being refracted by ice crystals in the atmosphere, the Moon Halo is visible to the naked eye and is, in a roundabout way, related to the Rainbow. In fact you can faintly work out the rainbow colours in the Halo, albeit inverted. Conditions have to be perfect to see a Moon Halo, subsequently one of this clarity is quite rare.
This photo is doubly rare as it was taken of a Blue Moon, the modern meaning being a second full moon in a calendar month. The phrase ‘Once in a Blue Moon’ is intended to denote something with rarity, though in reality Blue Moons occur once every 2-3 years. None the less, this adds rarity to the provenance of the image, even thought it would have been much cooler if the moon had actually been blue!
This Atmospheric image was taken near Zhongshan Station in Antarctica. What looks like stars in the image are actually snowflakes near the camera, illuminated by the flash.