天王星 月惑星研究会 関西支部
Uranus Image 2004/07/04(UT)
Paolo R. Lazzarotti,Keck
Paolo R. Lazzarotti (250mm Newton : Lumenera LU075M)
[Paolo R. Lazzarotti : Massa-City,Italy]
November 16, 2004 | If you had to vote for the most boring planet, you might pick Uranus. Unenhanced Voyager 2 images from its 1986 flyby revealed a bland, monochromatic, turquoise countenance with few clouds or belts. But recent near-infrared images from the 10-meter Keck II telescope in Hawaii demonstrate the old maxim that first impressions can be deceiving.
The images, taken in 2003 and 2004 with adaptive optics to counter atmospheric blurring, revealed dozens of discrete clouds, which is more than the total seen in all previous observations combined up to the year 2000. The clouds vary in size, brightness, and longevity, proving that Uranus has a dynamic and complex atmosphere after all.
In the northern hemisphere, the largest group of atmospheric features ever observed on Uranus ? a narrow, 29,000-kilometer-long (18,000 miles) cloud complex ? disappeared in only one month. Teams led by Lawrence A. Sromovsky (University of Wisconsin) and Heidi B. Hammel (Space Science Institute) have documented wind speeds exceeding 225 meters per second (about 500 miles per hour) ? the fastest yet recorded on Uranus. "Records are breaking as fast as we can take the data," says Hammel.
[Keck Observatory in Hawaii]