02-20-06

The source of star dust

AMES, Iowa -- NASA's Stardust mission just traveled seven years and 2.88 billion miles to bring space dust back to earth laboratories.

Lee Anne Willson, a University Professor of physics and astronomy at Iowa State University, has been working for 35 years to understand the stars that produce some of that dust.

Willson calls her work "stellar gerontology" because she studies red giants, the stars that expand and burn red and relatively cool as they move through the final stages of their life cycles.

Willson presented some of her research findings at the Annual Meeting of the American Association for the Advancement of Science in St. Louis on Monday, Feb. 20. She also addressed and helped organize a press briefing at the meeting titled, "Stardust: Solar System Birth and Death."

The press briefing also featured Don Brownlee, a professor of astronomy at the University of Washington in Seattle and the lead scientist for the National Aeronautics and Space Administration's Stardust mission. The mission's capsule dropped to the Utah desert on Jan. 15 with what Brownlee estimated to be more than a million comet and interstellar dust particles. Scientists will study the dust to learn more about comets and the origins of the solar system.

Willson said the origins of star dust are red giant stars characterized by:

• Super size. Their stellar radius is about the size of earth's orbit.

• Changing brightness. Their brightness varies dramatically over the course of a year-long cycle.

• High luminosity. They radiate several thousand times more power into space than the sun.

Willson said the variability of those stars is fundamental to dust formation. The variability produces shock waves which cause gasses to expand and cool very rapidly. That creates the conditions that allow dust formation closer to the star than would otherwise be possible. Recent observations of translucent molecular shells around red giants provide confirmation of Willson's theoretical analysis.

"These dust particles start their journeys in my stars and end up in the solar system," Willson said.

And that's a big deal to all of us. Willson said some of that dust came together some 4.6 billion years ago to create earth.

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