Caption: Near-infrared images from the Keck II telescope show the planet Uranus in 2005 (left), with the rings at an angle of 8 degrees, and at equinox in 2007 (right pair), with the planet's ring system edge-on. In all images, the south pole is at the left and the equator is directly below the rings. Uranus, which has an 84-year orbit around the sun, has seasons that last twenty-one years. With the aid of new imaging technologies and telescopes, scientists had their best chance to observe the change of seasons on the distant planet and to look for seasonal effects on some of the solar system's most mysterious weather features. One curiosity is the massive cloud structure in the planet's southern hemisphere (near the bright band), which moved 5 degrees north of its position in the 2005 Keck image. It is possible that seasonal forcing may be influencing the cloud feature, pushing it to a new dynamic state that may ultimately result in the feature's dissipation. The southern bright band itself declined in brightness between 2005 and 2007, while a new northern band brightened, consistent with the expectation that the bands will completely reverse by the next equinox in 42 years. The extremely bright northern feature seen in 2005 is thought to be the same as the bright features seen at the same latitude in 2007. The brightest ring seen in 2005 is not visible in these 2007 images because they are taken on the dark side of the ring system, on which only translucent rings can be seen. The small bright spots in the ring plane are satellite images.
Date: 2007
Credit: Imke de Pater, University of California, Berkeley; Heidi Hammel, Space Science Institute; Lawrence Sromovsky and Patrick Fry, University of Wisconsin-Madison. Obtained at the Keck Observatory, Kamuela, Hawaii.