4/23/01

Dawn Levy, News Service (650) 725-1944; e-mail: dawnlevy@stanford.edu

Astronaut and physicist Loren Acton to deliver Bunyan Lecture

Astronaut and solar physicist Loren Acton will deliver the 21st annual Bunyan Lecture at 7 p.m. Wednesday, May 2, in Terman Auditorium. The talk, which is free and open to the public, is titled "The Magnetic Personality of the Universe." Stanford's Astronomy Program in the Physics Department sponsors the Bunyan Lectures, which are intended to bring the latest findings in cosmology research to the public and explore their impact on society.

"The study of magnetism has been a dominant factor in the destiny of the human species," Acton said in a phone interview. "Our lives have been changed by electronics. What happens to us as people is often determined by our ability to control, understand and use electronic forces."

Scientists have made a number of discoveries recently about magnetic fields in space, he said. Acton's own work revolves around the largest magnetic laboratory in our collective backyard -- the sun. A professor of physics at Montana State University in Bozeman since 1993, Acton leads a research effort to monitor changes in the sun's blistering-hot outer corona. Temperatures in the corona can exceed 1 million degrees, Acton said, and the heat induces atoms in the corona to emit X-rays. Acton helped to design and build an X-ray telescope that monitors these emissions. The telescope orbits the Earth as part of a Japanese satellite mission called YOHKOH, which means "sunbeam."

YOHKOH has taken more than 4 million pictures of the sun since its launch a decade ago. The YOHKOH team anticipates continuing the observations until 2008, when the satellite is projected to reenter the Earth's atmosphere. Acton said study of the solar corona over a long period of time lets researchers link coronal changes to the solar cycle, in which the sun's magnetic field swaps north with south every 22 years. Acton will present results from the project to the scientific community at 4 p.m. Thursday, May 3, in a technical talk titled "Solar Cycle Dependence of Coronal Activity as Observed by Soft X-ray Telescope on YOHKOH." The talk will be held in the second floor conference room of the Varian Building.

The allure of space had a lot of influence on Acton when he was in school. Space science opened up a host of new ways to explore the world. "The space program was just taking off," he said. "It was like taking off your dark glasses ­ you could see the universe in a way that you'd never been able to before."

His doctoral dissertation at the University of Colorado in 1965 dealt with very early measurements of solar X-rays. "It was so much fun, I've been doing it ever since," he said.

Acton worked in Palo Alto at Lockheed research labs from 1964 to 1993. He was working there in 1977 when NASA accepted Lockheed's proposal for a space shuttle experiment. In July 1985, Acton found himself in orbit, operating solar telescopes during eight days on the space shuttle Challenger. Escaping the Earth's atmosphere is critical for making precise observations, as atmospheric interference can clutter up data. "By putting a telescope in space, every picture was perfect," Acton said. "And when you saw things happen, you had to believe them and try to interpret them."

The space experiments suggested that gas motions in the sun's outer atmosphere are strong enough to push around the magnetic field, Acton said. "This probably results in energy storage in the corona," he said, which may contribute to making the corona hotter than the visible surface of the sun.

In addition to his work on the X-ray experiment on YOHKOH, Acton has been principal investigator on many NASA research programs, including eight rocket experiments, all in the area of solar X-ray studies.

Among his many awards, Acton has received the 2000 Hale Prize for long-term contribution to solar physics from the American Astronautical Society, the 1993 NASA Exceptional Scientific Achievement Medal, the 1988 Robert E. Gross Award for technical excellence at Lockheed Corp. and the 1986 Spaceflight Achievement Award of the American Astronautical Society. He also holds an honorary doctorate from Montana State University.

Katie Greene is a science writing intern with Stanford News Service.

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By Katie Greene