Nov. 11, 2004 — Uranus is not the static, boring orb once thought, new pictures of the planet by the Keck II telescope in Hawaii reveal.

In fact, the sharpest photos ever of the planet from a ground-based telescope show storm clouds brewing as the seasons change and the rings brighten at the third-to-last planet in the solar system.

The beginning of autumn in the planet's southern hemisphere and the arrival of spring in the north is a sight never before seen with high-resolution telescopes like the Keck, since it happens once every 84 years as the planet slowly orbits the sun.

"When the Voyager 2 spacecraft flew by Uranus in 1986, it saw almost no discrete cloud activity — you could literally count the number of discrete clouds on your fingers: 10!" said Heidi B. Hammel of the Space Science Institute in Boulder, Colo., who, with Imke de Pater, an astronomy professor at the University of California, Berkeley, has been studying Uranus with the Keck telescope since 2000.

"Most astronomers decided that Uranus was a boring, static planet," Hammel said in a press release. "What we are seeing now is the opposite, that actually there are changes, and they are visible to Keck and the Hubble Space Telescope."

With Keck's super-sharp optics system, the duo also found an 11th ring around Uranus, a narrow sheet of rocky debris. The ring, the innermost of its siblings, is about 3,500 kilometers (2,200 miles) wide and centered about 39,600 kilometers (24,600 miles) from the planet core, according to the release. The ring is now visible because its edge-on position to the sun and Earth reflects light.

The team also discovered that Uranus' nine main rings are comprised of a single layer of particles, something not found in other rings.

"We had never seen such an odd configuration in other ring systems," said de Pater. "Rings in other systems, like Saturn's rings, are usually depicted as being many particles thick. Uranus' ring system is unique in this respect."

De Pater, Hammel and colleague Seran Gibbard of Lawrence Livermore National Laboratory report their observations this week at the American Astronomical Society's Division for Planetary Sciences meeting in Louisville, Ky.

Astronomers think the bands and clouds on Uranus are made of methane that is condensing into crystals in the atmosphere, which is mostly hydrogen and helium, the press release said. The planet's structure is thought to be a rocky core, surrounded by water, ammonia and methane slush.

During the first close-up observations of Uranus, made 18 years ago by the Voyager spacecraft, the probe determined that the planet's day lasted 17 hours and 14 minutes.

The team also reported clocking the fastest winds ever recorded on Uranus. Roaring along between 107 and 111 meters per second (240 and 260 miles per hour), the winds were measured in October 2003 on the northernmost parts of the planet visible at that time.