Astronomy Picture of the Day

Explanation: What are those colourful rings around the Moon? A corona. Rings like this will sometimes appear when the Moon is seen through thin clouds. The effect is created by the diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colours has different wavelengths, each colour diffracts differently. Lunar Coronae are one of the few colour diffraction effects that can be easily seen with the unaided eye. The featured image of a lunar corona was captured around last week's full Super Moon from near Knight's Ferry, California, USA. To the right of the full Moon is the giant orange star Botein. Similar coronae that form around the Sun are typically harder to see because of the Sun's great brightness.