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Williams College faculty/student team travel to study solar eclipse

March 21, 2006

A team of Williams College faculty and students is preparing to scientifically observe the total eclipse of the Sun that will sweep across the far side of Earth on March 29. Six undergraduates are joining Jay Pasachoff, Bryce Babcock, and Steven Souza of the astronomy and physics departments, who have worked together on a series of expeditions, most recently to study Pluto and its moon Charon.

The expedition is to Kastellorizo, a small island east of Rhodes in the Greek Dodecanese. Aside from Cyprus, it is the farthest eastern point of Europe, so many eclipse watchers are expected to travel there. The Williams group will be on site a week in advance to set up, test, and align its nearly ton of equipment. They are working closely with Professor John Seiradakis of the Aristotelian University of Thessaloniki, continuing a collaboration begun with joint observations there of the 2004 transit of Venus.

Pasachoff, chair of the International Astronomical Union's Working Group on Eclipses, will be observing his 42nd solar eclipse. He is Field Memorial Professor of Astronomy and director of the Hopkins Observatory at Williams. Babcock is coordinator of science facilities and staff physicist; Souza is instructor of astronomy and observatory supervisor. They last observed an eclipse in 2002 in Australia. The total solar eclipses since then have been visible only from Antarctica in 2003 and the mid-Pacific in 2005, preventing the use of complex equipment.

The student participants are Megan Bruck '07 of Tempe, Ariz., Paul Hess '08 of Simsbury, Conn., Shelby Kimmel '08 of Newton, Mass., Jesse Levitt '08 of Natick, Mass., Amy Steele '08 of Orlando, Fla., and Anna Tsykalova '08 of Ardmore, Pa. The group devoted time during Williams' January Winter Study Period to test the expedition's equipment.

The eclipse will start at dawn on the eastern tip of Brazil and sweep across the Atlantic and over western and northern Africa, where many astronomers will observe from southern Libya. The path of totality will then cross the Mediterranean and Kastellorizo, less than two miles off the Turkish coast. After passing over the middle of Turkey, the path of totality will continue across central Asia before ending at sunset in northwestern Mongolia. A partial eclipse will be visible from all of Europe and most of Africa and Asia.

The Williams team will have three minutes to capture its observations of the Sun's corona, the faint outer halo of million-degree gas that is hidden by the sky except during a total eclipse. That length of time is relatively long compared with the approximately 30 seconds afforded by the most recent eclipses.

Two of the group's experiments involve searching for the mechanism that heats the solar corona to millions of degrees by taking rapid series of images with new electronic cameras through specially designed filters. One filter passes a narrowly defined color in the green portion of the light spectrum and the other passes a narrowly defined color in the red. Each is emitted by gas in the corona from iron that has been heated to such high temperatures that it has been stripped of 13 or 9 electrons, respectively, from its normal 26.

A third experiment uses a filter that provides an even more narrowly defined coronal color. Known as a Fabry-Perot, it was designed and built by the Johns Hopkins University Applied Physics Laboratory for David Rust, a solar astronomer there. Rust and his colleague Matthew Noble will be in Kastellorizo. Williams alumnus Rob Wittenmyer '98, now a graduate student in astronomy at the University of Texas, also will work with the team on site.

A fourth experiment involves a specially built telescope that matches one now defunct aboard the Solar and Heliospheric Observatory (SOHO), a satellite built and operated by the European Space Agency and NASA. Both organizations have arranged with Pasachoff to receive a digital image immediately after the eclipse, to merge with their own spacecraft images and to distribute to the public. Bernhard Fleck, SOHO project scientist, will be on site with the Williams team.

The group will capture a further variety of digital and film images. They will include work by several veterans of previous Williams eclipse expeditions, including Lee Hawkins from Appalachian State University and Jonathan Kern of the Large Binocular Observatory in Tucson, Ariz. Kern will capture images with a camera modified to flatten the extensive dynamic range of the corona to enable the delicate coronal structure to show on a single piece of photographic film.

In Kastellorizo, the Williams team will also be joined by Seiradakis and two of his students, along with Margarita Metaxa of Athens, who works with Pasachoff on the International Astronomical Union's Commission on Education and Development, and two of her high-school students.

Pasachoff maintains the Website http://www.eclipses.info that links to various eclipse-related resources. With the assistance of Milos Mladenovic of Williams' office of information technology, he has posted details of all the scientific experiments planned for March 29 at sites in Libya, Egypt, Greece, and Turkey.

Williams College