Public Release: 

The Windy Planet

University of Wisconsin-Madison

TUCSON, Ariz. _ A new view of Neptune's wild weather, where winds whip around the equator at speeds of nearly 900 mph, has been captured by NASA's Hubble Space Telescope and the space agency's Infrared Telescope Facility in Hawaii.

A team of scientists led by Lawrence Sromovsky of the University of Wisconsin-Madison's Space Science and Engineering Center made simultaneous observations of Neptune with both telescopes, providing high-resolution images of the clouds on a planet whose weather is among the most baffling in the solar system.

The new results, and a time-lapse movie showing a full 16.11-hour rotation of the distant planet, were presented here today at the annual meeting of the Division of Planetary Sciences of the American Astronomical Society.

The new view of Neptune, scientists hope, will provide fresh insight into the extraordinary weather on the eighth planet from the sun. The new results, says Sromovsky, will permit a comparison of details sent back to Earth by the Voyager probe seven years ago when some of the first details of Neptune's tempestuous weather were relayed back to Earth.

At the time, scientists obtained their first detailed insights into Neptune's weather, characterized by a powerful equatorial jet stream and storms that dwarf the Earth's most violent storms. One intriguing Voyager discovery, the Great Dark Spot, was a pulsating storm feature the size of the Earth that has since disappeared.

Sromovsky's team reports the observation of another dark spot in Neptune's northern hemisphere, but this may be the same feature observed last year by an MIT team. The new, more closely-spaced observations should enable scientists to tease out more details of Neptune's weather and obtain clues about the unknown forces that drive it.

The cause of Neptune's blustery weather is an enigma, said Sromovsky. On Earth, winds are driven by the sun's energy, which heats the atmosphere and oceans. On planets farther from the sun, like Neptune where the sun is 900 times dimmer, winds should be weaker.

"But despite its weak energy input from the sun and its own weak internal heat flux, Neptune's weather is among the most dynamic in the solar system with changes occurring on time scales ranging from minutes to decades," Sromovsky said.

By using both Hubble and the NASA Infrared Telescope facility on Mauna Kea, Hawaii, Sromovsky's team was able to observe the distant planet in a variety of wavelengths, each providing a different set of information about Neptune's clouds, their structure, and how they circulate.

By observing the planet's clouds and how they move, scientists can make more precise calculations of Neptune's wind speeds and directions.

In addition to Sromovsky, the team of scientists making the new set of observations includes Sanjay Limaye of the UW-Madison Space Science and Engineering Center; Kevin Baines and Glenn Orton of the Jet Propulsion Laboratory in Pasadena, Calif.; and Andrew Ingersoll of the California Institute of Technology.

_ Terry Devitt, (608) 262-8282,

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