Uranian features made picture perfect by UA scientist

Wildcat File Photo Arizona Daily Wildcat Photo Courtesy of Space Telescope Science Institute A recent Hubble Space Telescope view reveals Uranus surrounded by its four major rings and by 10 of its 17 known satellites. This false-color image was generated by Erich Karkoschka, a UA lunar and planetary research associate, using data taken Aug. 8 with Hubble's Near Infrared Camera and Multi-Object Spectrometer.

Erich Karkoschka, a University of Arizona lunar and planetary research associate, discovered new details of the four major rings and 10 of the 17 satellites that surround the planet.

Images of Uranus were taken by the Near Infrared Camera and Multi-Object Spectrometer, which was developed by the UA for the NASA Hubble Space Telescope.

The Near Infrared Camera and Multi-Object Spectrometer took 45 images during a four-day period in August, but certain details could not be distinguished.

Karkoschka superimposed three of the photos, each colored by a different filter, to create a more definitive Uranus image.

The filters displayed each image as blue, green and red to form the Uranus photo, but Karkoschka said the colors are artificial.

"If these three images had been taken with blue, green and red filters as is the case for the most digital cameras or films, you would have a true-color image," he stated in an e-mail. "Since these three images are at near-infrared wavelengths, it creates a false-color image."

Most scientific color images are false-color images because the most useful filters are rarely blue, green or red, he said.

After the proposal to photograph Uranus was approved last year, Karkoschka produced the image from three Hubble pictures taken Aug. 8.

Karkoschka's false-color image was released Wednesday on the World Wide Web.

Because of the detailed image, scientists can study Uranus' atmosphere more closely.

"(New Mexico State University astronomy associate professor) Mark Marley and I will determine where clouds and haze layers are in the atmosphere of Uranus, the altitude thickness, particle size and possible hints of their composition," Karkoschka said.

Heidi Hammel, a Massachusetts Institute of Technology research scientist, plans to measure cloud speeds, which will give information on how Uranus rotates.

Karkoschka is doing photometry on the rings and satellites. Photometry is the measurement of light intensity.

"The color and brightness will tell us specifics about the surface properties - it may tell us about their origin," Karkoschka said.

If the spectrums of the rings and moons are similar, then they could have the same origin.

"If they look different they can give scientists more hints about the processes of the Uranian system," he said.

The image's colors change based on how close objects are to the planet's surface.

"This way we can calculate more accurate altitudes of the planet features," Karkoschka said.

For example, green and blue areas show the clear part of the atmosphere where sunlight can shine through. Red indicates higher atmospheric altitudes.

"I was able to see two to three long, orange clouds between the yellow-green bands and five red clouds," Karkoschka said.

Karkoschka was a pioneer in developing such a detailed image of Uranus.

"I am the only one at the UA working on this," he said.

The full-color image can be seen on the Internet at www.stsci.edu or science.opi.arizona.edu.

Irene Hsiao can be reached via e-mail at Irene.Hsiao@wildcat.arizona.edu.