1. You have been travelling around the world for more than 30 years observing and recording solar eclipses. What has motivated you to do this? How did you end up becoming an expert on eclipses?
In my first month as a first-year student at Harvard, the Director of the Harvard College Observatory, Donald Menzel, took his freshman seminar, which included me, on an Eastern Airlines jet to see the total solar eclipse that passed over Boston's north shore. From our vantage point above the rain, we saw the eclipse. Obviously, I was stunned by its beauty and motivated by its science from that time onward. (And for those who might say that I just like to travel, I point out that I was motivated by an eclipse that passed within a few miles of where I was at school.)
I saw another eclipse in 1963, traveling to Canada with two other graduate students (just after I finished Harvard College and entered Harvard graduate school). Prof. Menzel and I planned some observations for the 1968 eclipse in Russia, but the Russian invasion of Czechoslovakia nixed those plans. In 1969-70, I was a postdoctoral fellow with Dr. Menzel at the Harvard College Observatory, in large part to work on the eclipse expedition to Mexico that we described in the August 1970 National Geographic Magazine, so that eclipse was really my first professional work on eclipses. I had done a Ph.D. thesis on other aspects of solar research by that time.
When I started at Williams College in 1972, finishing a postdoc at Caltech (where I am going on sabbatical starting September 1st), there was to be an eclipse on July 10, only 10 days after my Williams College appointment began. So while I was still at Caltech, I visited Williams and recruited four undergraduates to observe the eclipse with Prof. Menzel and me from Prince Edward Island. I have continued the tradition since of involving undergraduates; I have three with me in Siberia now.
2. How many eclipses have you seen? How many places have you travelled to in your quest to record eclipses?
This is to be my 47th solar eclipse, each in a different location.
3. You must have good stories about your expeditions. What is the most remote location you've ventured to? What is the most memorable trip you've taken?
I guess that where I am now is 11 time zones away from Williamstown, so it is about halfway around the Earth (around the northern hemisphere, at least). One can't get much farther away. The eclipse of 1984 was psychologically, perhaps, the most remote eclipse. I was in Papua New Guinea for that, in their Hula Peninsula for the eclipse itself, but I also got a chance to travel to settlements up the Sepik River. I had an interest in African and Oceanic art since I ran into Eliot Elisofon, a famous photographer who was photographing African dances and masks in the Sahara, on my 1970 trip to Agadez (Niger) and Timbuktu (Mali) to reconnoiter ahead of the 1973 eclipse whose totality passed near there. The buildings there looked like the famous intergalactic bar in Star Wars; perhaps the Star Wars bar was patterned after those mud buildings. Anyway, my research has taken me to some pretty interesting places.
We have also benefited in different countries by the expertise of colleagues. On my current expedition to Russia, we have with us Bill Wagner, a professor of Russian history at Williams College. Obviously, he speaks Russian very well, so he has been a tremendous help to us with various arrangements, getting through Moscow airport with our equipment, and so on. In Akademgorodok, we were preceded by half a day by Marek Demianski, who is now a visiting professor of astronomy at Williams College (and who is permanently a professor at the University of Warsaw). He is also fluent in Russian, and he already had various aspects of our situation in hand, in consultation with the Nestorenkos here, when we arrived a few nights ago. We have had similar help from colleagues on earlier expeditions. For example, Cappy Hill, then a professor of economics at Williams College (and now president of Vassar College) had done lots of academic work and also governmental advising in Zambia, and she came with us there for the 2001 eclipse. She and her contacts there were of tremendous help, especially with the logistics; but we also gave her a long Nikon lens and Nikon camera (1200 mm after doubling), borrowed from National Geographic's photo department, and she took great images for us. For the current eclipse, Nikon has lent us their latest camera, a D3, and the latest version of their 600 mm f/4 lens.
4. Do you run into the same people, both scientists and eclipse tourists, over and over? Is there a community of dedicated so-called eclipse chasers? What do you think motivates these folks? Can you briefly describe them, if they do exist?
Yes, there are communities -- usually quite separate -- of professionals and of amateurs who go to eclipses. I don't like the term "eclipse chasers," since we get to the eclipses BEFORE they occur. We can't chase after them; they move too fast.
I am unusual in knowing so many amateur astronomers, perhaps through my high-school background as an amateur astronomer and more recently since my having done the Peterson Field Guide to the Stars and Planets, which is used by many amateurs. I have some good eclipse images and information in the book, in addition to material about the rest of the heavens.
In the 1970's and 1980's the US National Science Foundation sponsored some group expeditions, notably to Loiengalani in the Northern Frontier District of Kenya in 1973 and to Tanjung Kodok in Eastern Java in 1983. So many eclipse professionals from the US collaborated then. I myself, in my role as Chair of the International Astronomical Union's Working Group on Eclipses, coordinated a group expedition to the mountains above Arica in Chile near the Peruvian and Bolivian borders.
5. Why did you pick Russia for this eclipse? What do you hope to see (or discover) there?
This eclipse path goes over Novosibirsk, the third most populous city in Russia, so we could get our personnel and equipment here directly. And the sun is higher in the sky than it is along the path in Mongolia in China, with much better weather forecasts than earlier in the path near the North Pole or northern Siberia. So Novosibirsk seems to me to be the best place to observe this eclipse, given that we need electricity and other facilities for our professional equipment.
We have a series of scientific experiments. The main one is to observe the corona at high time resolution (that is, high cadence of about 5 times per second) through special filters that pass only emissions from the corona from gas at millions of degrees. In particular, there is a coronal "red line" from iron that has lost 9 of its normal 26 electrons and a coronal "green line" from iron that has lost half (13) of its normal 26 electrons), and it takes extremely high temperatures for so many electrons to be ejected from the atoms -- we say that those atoms are extremely highly ionized. There are several theories of how the corona gets to be so hot, given that it is above the everyday sun, which is at "only" about 6000 degrees Celsius), and we intend our observations of high-frequency coronal oscillations to help discriminate among theories.
We are also observing the corona at extremely high resolution, especially using special, new techniques of post-eclipse processing worked out by Prof. Miloslav Druckmuller of the Czech Republic along with Dr. Vojtech Rusin of Slovakia. We had a paper about our 2006-eclipse results that appeared in the Astrophysical Journal just last week, its July 20th issue, in which we were able to detect a plume near the pole of the sun move at about 500,000 miles per hour upward away from the sun. Gas ejected from the sun in the "solar wind" even reaches the Earth, and understanding ejections of gas from the sun, and how they are affected by the sun's magnetic field, can have an advantage for understanding how the sun affects the Earth.
6. What do you hope to see next year in China? What is special about that eclipse?
Each eclipse is different, and if you get only two minutes 20 seconds (this year) or 5 minutes 50 seconds (next year) to see something, you surely can use more time. The sun varies with the sunspot cycle -- more generally, the solar-activity cycle -- and we are at an extreme low in the sunspot cycle now. Most days, the sun is completely blank. That low level of sunspot activity shows that there is a low level of magnetic activity on the sun (which we can also see in observations from the Solar and Heliospheric Observatory and Hinode spacecraft), and low magnetic activity leads to a solar corona that extends much farther in the sun's equator than it does at the poles, where polar plumes of gas (such as the one in motion that we observed in 2006) are more prominent. There is already a prediction of the shape of the corona based on the existing solar magnetic field, measured as the sun continues to rotate, and such an equatorial extension of the
sun's shape is predicted.
Zoran Mikic, an American scientist, has already predicted the shape of the corona, with a forked appearance at the ends of the equatorial extensions. Our images will check his predictions, among many other things.
7. How do you use the data you collect?
It takes years for my students at Williams College and me to study the results and to make conclusions.
We report the results at meetings of the American Astronomical Society and the International Astronomical Union. And then we publish papers in scientific journals describing our results. In those ways, the astronomical community learns about our research.
8. You study the formation of coronal streamers, solar wind and other solar phenomena. How do these affect our planet?
A "solar wind" of particles from the sun hits the Earth. There is a "slow wind" and a "fast wind," obviously of different speeds (by a factor of about 2) that take days to reach Earth. The particles (and also x-rays and other forms of electromagnetic radiation that travel from sun to Earth in 8 minutes) cause magnetic storms on Earth, cause aurorae at the poles, and sometimes cause blackouts of radio communications and even of GPS signals. Obviously, we want to be able to predict such storms, and prediction involves understanding the basic mechanisms, which is part of what we are trying to do. Of course, we are addressing only particular aspects of the sun, but each scientist does whatever he or she can.
And we also know, from observations with the Chandra X-ray Observatory and other x-ray spacecraft, that billions of other stars also have coronas like the sun's. So the sun is a closeup example of phenomena that we find all over the Universe. I am working with Nancy Evans, Scott Wolk, and others at the Harvard-Smithsonian Center for Astrophysics to study x-ray emission from the coronas of a variety of stars in the star clusters h and chi Persei.
9. How has the technology changed over the years? Both in terms of how you personally record these events, but also what other people are now doing? How do your efforts complement other efforts, such as the Hinode spacecraft?
The advances in technology are fantastic. The electronic cameras we have are at least 100 times more sensitive than film, so an image we take in 10 seconds would have taken 1000 seconds or five minutes on film. We couldn't have made our high-cadence observations on film; it wouldn't have been sensitive enough. Further, advances in computers allow us to study the data in ways we couldn't manage before.
In addition, we have technology in space, such as telescopes on Hinode, TRACE (NASA's Transition Region and Coronal Explorer) and SoHO (the European Space Agency's and NASA's Solar and Heliospheric Observatory), that can observe many aspects of the sun, including the corona, but that can't observe the parts of the corona as well as we can, particularly not at high time resolution such as that we have. So we can now team up with the results from the spacecraft, putting everything together to get a fuller picture of the sun and how it works.
10. How is this research contributing to science, both in the short- and long-term?
Of course, studying the sun is studying a typical star, so everything we learn about the sun applies to billions of other stars. And the physical laws that we improve from our studies of the sun apply throughout the universe. They even apply on Earth: I hope that one day we will have fusion reactors to supply us energy on Earth, duplicating not only the nuclear processes of the sun's interior but perhaps also duplicating the holding extremely hot gas in a magnetic field that takes place routinely in the solar corona.
11. What have you learned, and what has the scientific community in general, learned since you started working in this field?
That's a whole book -- and I wrote some! Leon Golub (who is a solar scientist at the Harvard-Smithsonian Center for Astrophysics, who, among other things, built the x-ray telescope on Hinode and the telescope on TRACE) and I wrote Nearest Star: The Surprising Science of the Sun" for Harvard University Press. See: www.williams.edu/astronomy/neareststar.
We also did a more technical book, "The Solar Corona": www.williams.edu/astronomy/corona.
These books detail the advances in solar science over the years. We understand the sun much better than we did before -- but not as well as we would like. I can't even tell you when the number of sunspots on the sun will begin to rise.
12. What about this work do you enjoy most?
All of it. It's great to think about such an interesting object as our sun -- and to work with wonderful colleagues and students in studying it. I've had a long partnership with Bryce Babcock of Williams College; he's a brilliant instrumentation specialist, and he's in charge of the equipment on our eclipse expeditions. He's on the roof of the physics building here at the State University of Novosibirsk now as I sit at the computer answering your questions. He's working with two of our Williams College students in testing the equipment we brought with the new telescope drive of the university here which we helped them install yesterday. Igor Nestorenko and Allya Nestorenko of the State University of Novosibirsk and the Academy of Science's Budker Institute of Nuclear Physics are our hosts here, and it is a wonderful experience to work with them and to learn about what they do.
13. What has been the biggest challenge?
It is always a challenge to keep up with the latest research and to make sure that we are using the latest methods and the latest theoretical ideas to do the most important projects. And, of course, it is always a challenge to transport equipment halfway around the world and to have it still work.
14. Do you have plans to retire? What will you do in retirement?
I have no plans to retire. It would be nice to see Halley's Comet return in 2061, when I would be 118, and still be working away on interesting astronomical projects.
Other stories about Pasachoff's work that include more information about the science behind eclipses are at: