Complex Weather Of The Planet Uranus Revealed By The Keck Observatory
Thanks to a new technique being used by the Keck Observatory, some of the most detailed images ever taken of Uranus have been obtained. These images are giving researchers new insight into the complex weather and atmospheric conditions of a planet that has remained somewhat of a mystery since being discovered.
By using a new technique with the telescopes of the Keck Observatory, astronomers have created the most richly detailed, highest-resolution images ever taken of the giant ice planet. The images, taken in the near infrared, show aspects of the giant, icy planet that have never been observed before.
The new images have revealed that the weather there is more similar to the other large outer planets than was previously known, with “bands of circulating clouds, massive swirling hurricanes and an unusual swarm of convective features at its north pole,” a UC–Berkeley news release notes.
“This ‘popcorn’ appearance of Uranus’s pole reminds me very much of a Cassini image of Saturn’s south pole,” said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and one of the researchers.
The feature that de Pater is referring to is an enormous polar vortex that is surrounded by numerable features in the clouds indicating strong convection, “analogous to the heavily precipitating clouds encircling the eye of terrestrial hurricanes.” Previous research has suggested that something similar will be visible on Neptune, based upon Keck observations of that planet.
“Perhaps we will also see a vortex at Uranus’ pole when the pole comes in full view,” she said.
The reason that we don’t have much knowledge of Uranus is because of its vast distance from the Earth. It’s 30 times further from the Sun than the Earth is — even using the best telescopes that we currently have there is no detail visible.
But by combining numerous images that were taken by the Keck II telescope, the researchers were able to reduce all of the noise and focus on the weather features that had previously been indistinguishable. “The group used two different filters over two observing nights to characterize cloud features at different altitudes.”
The researchers found “that in the planet’s deep atmosphere, composed of hydrogen, helium and methane, winds blow mainly in east-west directions at speeds up to 560 miles per hour, in spite of the small amounts of energy available to drive them. Its atmosphere is the coldest in our solar system, with cloud-top temperatures in the minus 360-degree Fahrenheit range, partly due to Uranus’ great distance from the sun.”
“The sun is 900 times weaker than on Earth, so you don’t have the same intensity of solar energy driving the system as we do here,” said Sromovsky. “Thus, the atmosphere of Uranus must operate as a very efficient machine with very little dissipation. Yet it undergoes dramatic variations that seem to defy that requirement.”
One of the more interesting findings is that the large weather systems there act in ‘strange’ ways. Some of them stay only at certain latitudes and ‘undergo large variations in activity’. Some of the others, though, will move towards the equator, and greatly change in size and shape as they do.
“A key to understanding these behaviors was a better measurement of the wind field surrounding them. That required detecting smaller, more widely distributed features to better sample the atmospheric flow. The movement of these features? help scientists trace the planet’s pattern of blustery winds.”
So far, the new finding that stands out the most is the discovery of a ‘scalloped’ band of clouds, located somewhat south of the equator. The only theories put forward have been that it may be indicative of wind shear or atmospheric instability.
“This is new, and we don’t fully understand what it means,” said Sromovsky. “We haven’t seen it anywhere else on Uranus.”
Image Credits: Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater; Imke de Pater. UC Berkeley