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:
http://news.nationalgeographic.com/news/2002/12/1203_021203_solareclipse.html
http://news.nationalgeographic.com/news/2001/06/0620_eclipse.html