New images capture Uranus as it changes seasons

Washington, Oct 14 : A team of researchers from the University of Wisconsin-Madison has released new Keck II telescope images of the Uranus as it changed seasons.

With an 84-year orbit around the sun, it isn't often that planetary scientists have an opportunity to observe the change of seasons on Uranus, a planet some 19 times farther from the sun than the Earth.

But in 2007, the planet reached equinox, the point in time where the sun is directly over the planet's equator and what little sunlight the planet gets is distributed evenly over its northern and southern hemispheres, giving scientists their best opportunity to probe the seasonal dynamics of the ringed planet.

"The last time this happened, there were no instruments that could resolve any features on the planet," said Lawrence Sromovsky, the elader of the research team. "Now we can see what's going on," he added.

The new study, based on a set of Keck II observations, was intended to take advantage of the change of seasons on Uranus to better understand how the sun influences the planet's weather.

Sromovsky and his colleagues were especially interested in seeing how the change of seasons influenced the weather on Uranus.

According to Sromovsky, the study is challenging because the progress of the seasons is so slow on Uranus and the planet is so far away, but it is intriguing because the planet's equator is tilted at an unusually large 98 degrees from its orbit plane, as if it had been tipped on its side.

"This tilt gives it the largest seasonal forcing of any planet in the solar system," said Sromovsky. "On an annual average basis, the poles get more sunlight than the equator," he added.

The most recent Keck II images show changes in the brightness of cloud bands in the planet's northern and southern hemispheres as well as changes in two previously observed and apparently long-lived discrete cloud features.

One is a massive vortex that had been oscillating in Uranus's southern hemisphere, perhaps for decades, between 32 degrees and 36 degrees south latitude.

In 2004, the feature began drifting north and may soon dissipate, according to the new report.

"For two decades, it seemed like it was behaving in a very reliable way," said Sromovsky. "It may be that a change in the seasons has triggered it into a new dynamical state," he added.

The new images also gives the opportunity to measure Uranus's monster winds over a wide range of latitudes than was previously possible.

Winds on the planet can achieve speeds of up to 560 miles per hour.

ANI