UC Berkeley researchers demystify Uranus’ weather patterns

A new technique developed by a team of astronomers shows the two faces of Uranus, in previously unattainable detail, through the Keck II telescope in Hawaii.
Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater/Courtesy
A new technique developed by a team of astronomers shows the two faces of Uranus, in previously unattainable detail, through the Keck II telescope in Hawaii.

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The surface of Uranus has been nebulous to astronomers for years, but researchers at UC Berkeley and the University of Wisconsin-Madison have studied the planet’s weather patterns and gained some clarity as to what its surface looks like.

The team of researchers used infrared cameras on the telescopes at the W. M. Keck Observatory in Hawaii to take several high-resolution, overlapping images of the planet. The team then combined the images to discern weather features that were previously too difficult to notice, according to Lawrence Sromovsky, the project’s head researcher and a senior scientist at the University of Wisconsin-Madison.

“It’s really a simple idea actually, but it hasn’t been applied too often,” Sromovsky said. “This is the first time the technique is being used to learn about Uranus.”

From the images, the team discovered “popcornlike” cloud features on the north pole of Uranus, said Imke de Pater, a researcher on the team and chair of astronomy at UC Berkeley. De Pater said that these cloud features indicate convection at this stormlike region.

The researchers also discovered wind patterns on Uranus that revealed asymmetry of wind patterns at the poles, Sromovsky said. He added that the team’s most unusual discovery was a scalloped pattern of clouds south of Uranus’ equator, which could indicate atmospheric instability.

Uranus, the third-largest planet in the solar system, is composed of gas like Neptune and Saturn. While astronomers have been able to discern many features about the planet, such as its atmospheric composition of hydrogen, helium, and methane — which gives the planet its blue-green color — its distance from the Earth has prevented astronomers from learning about the planet’s wind patterns and cloud features. Until recently, the flyby of the planet by the Voyager 2 spacecraft in 1986 was the only chance astronomers had to study the planet close-up.

“Other planets have had several flybys, and we’ve been able to learn a lot about their features,” Sromovsky said. “From the Voyager, we were only able to discern maybe eight cloud features on Uranus, and we are limited to learning about the planet through ground observations.”

According to de Pater, another reason the cloud features on Uranus have been too faint to notice is due to the relatively low contrast in brightness between the planet and its clouds.

Because of the difficulty to discern the planet’s features, researchers tried the new technique, which is commonly used to interpret the morphology of clouds in the Earth’s atmosphere, according to James Graham, a professor of astronomy at UC Berkeley.

“This multi-filter technique is useful whenever a planetary atmosphere contains molecules with distinctive absorption bands,” Graham said in an email. “On the giant planets, filters matched to the absorption bands of methane are useful. On the terrestrial planets carbon dioxide and water, for example, could be used.”

Pooja Mhatre covers research and ideas. Contact her at [email protected].