Astronomy Picture of the Day

Explanation: Yes, but how many dark clouds have a multicoloured lining? Pictured, behind this darker cloud, is a pileus iridescent cloud, a group of water droplets that have a uniformly similar size and so together diffract different colours of sunlight by different amounts. The above image was taken just after the picturesque sight was noticed by chance by a photographer in Ethiopia. A more detailed picture of the same cloud shows not only many colours, but unusual dark and wavy bands whose origins are thought related to wave disturbances in the cloud.