The Total Solar Eclipse of June 21, 2001

Scientific Experiments at the 1999 and 2001 Total Solar Eclipses: The Williams College Expeditions

LUSAKA, Zambia, June 21, 2001 The moon's shadow raced across southern Africa today delighting residents, tourists, and scientists, including an expedition from Williams College. At 1:09 pm the moon totally blocked the sun over Lusaka for three minutes and 14 seconds, providing a spectacular show of light that drew cheers from Zambians and visitors gathered on rooftops and fields across the city.

Researchers were equally excited with the first total eclipse of the millennium. "The sky was as clear as I have ever seen it at a total eclipse, the best since 1970," said Williams Professor of Astronomy Jay M. Pasachoff. "There wasn't a cloud in the sky, giving perfect conditions for our scientific observations. We were studying the solar corona, the outer layer of the sun that is ordinarily hidden behind the blue sky. The total eclipse took away the blue sky for three minutes this afternoon, giving us a view of the corona.

"We had a dozen Williams College students with us," said Pasachoff, "and they played a major role in setting up and operating the equipment. We have lots of data in our computers, recorded with our electronic cameras in digital format, and will have lots to study when we get back to Williamstown.

Pasachoff, chair of the Working Group on Eclipses of the International Astronomical Union (IAU), was observing his 32nd eclipse and he is already making plans for a scientific expedition to Ceduna, Australia, for the next one, which will take place on December 4, 2002.. He chairs the Subcommittee on Public Education at the Time of Eclipses of the IAU's Commission on Education and Development. He wrote the "Peterson Field Guide to the Stars and Planets" in addition to astronomy texts. He is co-author, with Leon Golub, of the trade book "Nearest Star: The Surprising Science of Our Sun," recently published by Harvard University Press.

The Williams group conducted three experiments at two locations in the Zambian capital. One of the experiments mapped the temperature of a quadrant of the sun's corona, the outermost layer of its atmosphere, which can attain four million degrees Fahrenheit (about two million Celsius) though its surface is only 11,000 degrees Fahrenheit (about 6,000 Celsius).

A second experiment was conducted in collaboration with scientists at NASA's Goddard Space Flight Center and the U.S. Naval Research Laboratory. The Williams group took images of the solar corona during the eclipse for comparison with images captured by the Extreme-ultraviolet Imaging Telescope and the Large Angle Spectroscopic Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory (SOHO) in space.

In a third experiment, the Williams scientists measured the polarization of the outer corona for comparison with measurements from the LASCO and Ultraviolet Coronagraphic Spectrometer aboard SOHO. The UVCS observations are in collaboration with scientists from the Harvard-Smithsonian Center for Astrophysics.

A fourth experiment, to look for waves in loops of gas at the edge of the sun, failed when a computer controlling its electronic detector stopped accepting commands.

The group spent months planning and nine days setting up and testing equipment on site, all in preparation for the three minutes of totality. The corona is visible from earth only while the sun is totally eclipsed.

Williams has a rich history of scientific expeditions, including the first ever sent by an American college, in 1835 to Nova Scotia. This month's expedition includes ten current or recently graduated Williams students and one student from Swarthmore College (on an exchange program with Williams). Participating on site were Daniel B. Seaton '01, Gabriel B. Brammer '02, Shoshana C. Clark '02, Bethany E. Cobb '02, D. Michael Gioiello '02, Kate Gibbons '03, Christopher D. Holmes '03, Kristen L. Shapiro '03, and Davy Stevenson '04, as well as Keck exchange student Roban Kramer (Swarthmore '03) and alumnus Rob Wittenmyer '98. Other faculty and staff from Williams are Bryce A. Babcock, coordinator of science facilities; Stephan E. Martin, supervisor of the Hopkins Observatory; Catharine B. Hill, provost, professor of economics, and an expert on Zambia; and James G. Kolesar, director of public affairs. Taking part as medical officer is Williamstown physician Paul E. Rosenthal. They were assisted by Phyllis Babcock, Emily Babcock of Drury H.S., and John Kildahl of Mt. Greylock Regional H.S. Joining them in Lusaka were other U.S. scientists and scientists from Great Britain, India, Malaysia, Slovakia, and Venezuela.

The expedition is supported by the National Science Foundation, the National Geographic Society, the Keck Northeast Astronomy Consortium, the Massachusetts Space Grant Consortium, the Science Laboratories at Williams College, and the Safford Fund, Brandi Fund, and Rob Spring Fund at Williams.

Images from the 1999 expedition are available at http://www.williams.edu/astronomy/eclipse1999/1999total/index.html.

References:

Jay M. Pasachoff, Peterson Field Guide to the Stars and Planets (Houghton Mifflin, 2000)
Leon Golub and Jay M. Pasachoff, Nearest Star: The Surprising Science of Our Sun (Harvard University Press, 2001). Just published.