Extreme Storms Shake Things Up on Uranus

Things are shaking up on the normally boring, blue dot that is Uranus with a series of extreme storms on its surface, according to researchers. These enormous cloud systems are so bright in fact, that for the first time ever even amateur astronomers can see them through the haze of the planet's blue-green atmosphere.

"The weather on Uranus is incredibly active," study leader Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, said in a statement.

"This type of activity would have been expected in 2007, when Uranus's once-every-42-year equinox occurred and the Sun shined directly on the equator," noted co-author Heidi Hammel. "But we predicted that such activity would have died down by now. Why we see these incredible storms now is beyond anybody's guess."

Using the W. M. Keck Observatory in Hawaii back in early August, de Pater, Hammel and their colleagues detected eight storms in all on Uranus's northern hemisphere. One was even the brightest storm ever witnessed on Uranus, seen at a wavelength of 2.2 microns, and accounted for 30 percent of all light reflected by the rest of the planet at this wavelength. Subsequent observations by the Hubble Space Telescope showed that the storm system spanned a distance of more than 9,000 kilometers (5,760 miles).

Once word got out of the storm parade, avid planet-gazers took to their telescopes to get a look for themselves. One such amateur astronomer, Frenchman Marc Delcroix, could not be more excited.

"I was thrilled to see such activity on Uranus," he said. "Getting details on Mars, Jupiter or Saturn is now routine, but seeing detail on Uranus and Neptune is the new frontier for us amateurs and I did not want to miss that."

Though, as to be expected, the layman's telescope is nothing compared to the 10-meter Keck II telescope's observations that viewed Uranus's storms in near infrared. And the wavelength at which the extremely bright storm was viewed suggests that this feature is below the uppermost cloud layer of methane ice in Uranus's atmosphere.

Uranus, an ice giant about four times the diameter of Earth, is located 19 times farther from the Sun than our planet, and so being able to see any sort of detail on its surface is remarkable.

De Pater and her colleagues, who have been following Uranus for more than a decade, believe the observed storms are caused by gases such as methane rising in the atmosphere and condensing into highly reflective clouds of methane ice.

Details of their findings were presented Nov. 12 at a meeting of the American Astronomical Society's Division of Planetary Sciences in Tucson, Ariz.