Office of Public Affairs
Williams College
P.O. Box 676
Williamstown, MA 01267
Tel: 413-597-4277 Fax: 413-597-4158
Contact: Jay Pasachoff
Jay.Pasachoff@williams.edu
413-597-2105
FOR IMMEDIATE RELEASE: 12 FEBRUARY 1998
Science At The 1998 Eclipse: Heating Of The Solar Corona
WILLIAMSTOWN, Mass. -- A group of scientists and students from
Williams College will study the heating of the solar corona during the
total solar eclipse of Feb. 26.
Preparing to observe his 26th solar eclipse, Professor Jay M.
Pasachoff, its leader, described their experiments, which they will be
carrying out from Aruba.
Pasachoff is Field Memorial Professor of Astronomy and Director of the
Hopkins Observatory at Williams College, Williamstown, Massachusetts,
USA. He is also Chair of the Working Group on Eclipses of the
International Astronomical Union and Chair of the Astronomy Division
of the American Association for the Advancement of Science.
Two of Pasachoff's experiments will deal with the still open question
of how the corona, the outermost layer of the sun's atmosphere, can
reach a temperature of two million degrees Celsius (about four million
degrees Fahrenheit), even though the everyday surface of the sun below
it is only 6,000 degrees Celsius (about 11,000 degrees Fahrenheit). A
third experiment is in liaison with scientists in charge of an
experiment on the Solar and Heliospheric Observatory (SOHO)
spacecraft. The experiments are in collaboration with Dr. Bryce
Babcock, staff physicist at Williams College.
The observations are possible only during the brief minutes of a total
solar eclipse, when the everyday sun is hidden by the moon, allowing
the faint corona to be observable from earth. On ordinary days, the
corona is hidden by the blue sky, since it is about a million times
fainter than the layer of the sun we see shining every day, the
photosphere.
Pasachoff, together with Dr. Leon Golub of the Harvard-Smithsonian
Center for Astrophysics in Cambridge, Massachusetts, recently
completed the first textbook about the solar corona to be written in
decades; it was published last summer.
The first experiment is a search for rapid oscillations in the corona,
with periods of about one second. Pasachoff has developed techniques
over the last two decades to observe in the so-called "coronal green
line," a color in which the corona emits light especially strongly,
with time resolution so fast that such short periods can be
detected. Oscillations with periods in that short range are predicted
by some theories that hold that the extreme coronal heating is caused
by vibrations of magnetic loops. The loops of gas, held in place by
the sun's magnetic field, have been observed, and the question is
whether their vibrations bring enough energy into the corona to heat
it sufficiently. The experiment is supported by a grant from the
Atmospheric Sciences Division of the National Science Foundation.
The second experiment is a map of the temperature of the corona, using
a technique of comparing electronic images of the corona taken at
special ultraviolet wavelengths. Following theoretical work, these
wavelengths are chosen to include two such at which the difference
between the shape of the everyday sun's spectrum and the corona's
spectrum is especially striking. The experiment is supported by a
grant from the Committee for Research and Exploration of the National
Geographic Society.
The third experiment is to image the solar corona during the eclipse
at the same scale and with the same green filter as a filter in the
coronagraph experiment on board the Solar and Heliospheric Observatory
(SOHO). This observation is in collaboration with Dr. Guenter
Brueckner of the Naval Research Laboratory, principal investigator of
that experiment, LASCO (Large Angle Spectrographic Coronagraph). The
comparison of the eclipse image with an image taken with one of
LASCO's coronagraphs will provide a calibration of how much light is
scattered in the process of making an artificial eclipse on board the
spacecraft. Such artificial eclipses cannot quite match the quality
of a natural eclipse, in which the moon hides the sun's light before
it reaches a telescope. The comparison of the eclipse result with the
SOHO image taken at the same time should allow improvements in data
reduction of future SOHO images.
An unusual aspect of Pasachoff's experimental team is that it includes
so many undergraduate students, eight in total, all astrophysics
majors at Williams College: Timothy McConnochie, Johan Kongsli, Mac
Stocco, James Bates, Laura Brenneman, and Craig Westerland. They are
supported by the NSF and National Geographic grants; by the Keck
Northeast Astronomy Consortium, a group of eight colleges whose
astronomical student research is supported by the W. M. Keck
Foundation; and by the Safford Fund, set up by his descendants in
honor of the second director of the Hopkins Observatory, Truman Henry
Safford. Also through the Keck grant, undergraduates Carolina Artacho
Guerra of Bryn Mawr College and Lisa Reinker of Wellesley College will
participate in the expedition.
Scientific staff also include Lee Hawkins of Wellesley College;
Stephan Martin of Williams College; and Jonathan Kern, an optics
designer from New Orleans. Also participating in the scientific work
are Prof. Joseph Hollweg of the University of New Hampshire;
Prof. Edw. S. Ginsberg of the University of Massachusetts Boston; and
Dr. Donald Lubowich of Hofstra University and the American Institute
of Physics.
The main team will spend two weeks on site in Aruba setting up,
aligning, and testing the ton of equipment they will bring. They will
arrive in Aruba on February 15.
References: Donald H. Menzel and Jay M. Pasachoff, Peterson Field
Guide to the Stars and Planets (Houghton Mifflin, updated 1997); Jay
M. Pasachoff and Michael Covington, Cambridge Guide to Eclipse
Photography (Cambridge University Press, 1993); Fred Espenak and Jay
Anderson, NASA Reference Publications 1383 for the 1998 eclipse and
1398 for the 1999 eclipse; Leon Golub and Jay M. Pasachoff, The Solar
Corona (Cambridge Univ. Press, 1997). Jay M. Pasachoff, 1973, "The
Solar Corona," Scientific American 229, #4 (October), 68-79. Donald
H. Menzel and Jay M. Pasachoff, 1970, "Solar Eclipse," National
Geographic 138, #2 (August), 222-233. Jay M. Pasachoff, 1992, "The
Darkness That Enlightens," National Geographic 181, #5 (May), 36-37.
For more information, call:
Prof. Jay M. Pasachoff
Williams College-Hopkins Observatory, Williamstown, MA 01267
Phone: 413 597 2105; Fax 413 597 3200; home 413 458 8346
e-mail: jay.m.pasachoff@williams.edu or
http://www.williams.edu/Astronomy/IAU_eclipses
During the eclipse expedition
February 16-28
The Mill Condominium, J.E. Irausquin Blvd. 330, Palm Beach, Aruba
Phone 011 297 8 67 700; fax 011 297 8 67271
Also February 23-28
Hyatt Regency Aruba, L.G. Smith Blvd #85, Palm Beach, Aruba
Phone 011 297 8 61234; fax 011 297 8 61682
Williams College is consistently ranked one of the nation's top
liberal arts colleges. Founded in 1793, it is the second oldest
institution of higher learning in Massachusetts. The college of
2,000 students is located in Williamstown, which has been called
the best college town in America. You can visit the college in
cyberspace at http://www.williams.edu
Last Modified by ALG on March 5, 1998.
Eclipse
