Astronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2003 March 11 Iridescent Clouds Credit & Copyright: Arne Danielsen Explanation: Why would clouds appear to be different colors? A relatively rare phenomenon known as iridescent clouds can show unusual colors vividly or a whole spectrum of colors simultaneously. These clouds are formed of small water droplets of nearly uniform size. When the Sun is in the right position and mostly hidden by thick clouds, these thinner clouds...