ASTRONOMY DEPARTMENT AND THE HOPKINS OBSERVATORY

The department enrolled the most astrophysics majors ever: 8 juniors in the class of ‘01 and 4 seniors in the class of ‘00. Seniors are Rebecca Cover ‘00, Sara Kate May ‘00, Kevin Russell ‘00, and Chris Spence ‘00. Juniors are Daniel Seaton ‘99, Joey Shapiro ‘99, Misa Cowee ‘99, Darik Velez ‘99, Brad Slingerlend ‘99, Joel Iams ‘99, Duane Lee ‘99, and Matthew Silver ‘99. See http://www.williams.edu/Astronomy/astromajors.html.

A major activity was the analysis of data from the expedition to the total solar eclipse of February 26, 1998. Tim McConnochie ‘98 and Kevin Russell ‘00 worked on this data during the summer of 1998. In particular, they were working with Prof. Pasachoff in a study of the source of the heating of the solar corona to temperatures of millions of degrees.

Pasachoff was awarded grants from NASA and from the National Geographic Society for his expedition to the total solar eclipse of August 11, 1999. These grants, in addition to an earlier grant from the National Science Foundation, enabled him to take a team including 12 undergraduate students and recent alumni. The grants are from NASA’s Guest Investigator Program for the Solar and Heliospheric Observatory spacecraft, from the Committee for Research and Exploration of the National Geographic Society, and from the Atmospheric Sciences Division of the National Science Foundation. The experiments were conducted in collaboration with Dr. Bryce Babcock, staff physicist at Williams College. Prof. Pasachoff also received an eclipse grant from NATO, as a liaison among the U.S., U.K. and Romania. It is held jointly with Dr. Magda Stavinschi of the Astronomical Institute in Bucharest and with Dr. Allan Ridgeley of the Rutherford Appleton Laboratory in the U.S. The grant is for 255,000 Belgian francs.

Two of the experiments deal with the still open question of how the corona, the outermost layer of the sun’s atmosphere, can reach a temperature of 2 million degrees Celsius (about 4 million degrees Fahrenheit), even though the everyday surface of the sun below it is only 6,000 degrees Celsius (about 11,000 degrees Fahrenheit). The third experiment is in liaison with scientists in charge of an experiment on the Solar and Heliospheric Observatory (SOHO) spacecraft. The observations are possible only during the brief moments of a total solar eclipse, when the everyday sun is hidden by the moon, allowing the faint corona to be observed 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, is co-author of the first textbook about the solar corona to be written in decades; published in 1997.

The first experiment is a search for rapid oscillations in the corona, with periods of about 1 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 deliver enough energy into the corona to heat it sufficiently. The experiment was supported by a grant from the Atmospheric Sciences Division of the National Science Foundation for the 1998 eclipse, and a similar grant has been awarded for the 1999 eclipse.

The second experiment maps the temperature of the corona, using a technique of comparing electronic images of the corona taken at special ultraviolet wavelengths. Following theoretical work, three wavelengths are chosen to include points at which the difference between the shape of the everyday sun’s spectrum and the corona’s spectrum is especially striking. The experiment was supported at the 1998 and 1999 eclipses by grants from the Committee for Research and Exploration of the National Geographic Society.

The third experiment images the solar corona during the eclipse to compare with observations of the corona seen with the Extreme-ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO), in collaboration with scientists at NASA’s Goddard Space Flight Center. The features seen at the eclipse outside the solar disk are matched up with their bases seen on the disk with the EIT experiment. Further, the experiment uses a lens that gives an image at the same scale and with a green filter that matches a filter in one of the telescopes in the coronagraph system on SOHO. This observation was in collaboration with the late Dr. Guenter Brueckner of the Naval Research Laboratory in Washington, D.C. principal investigator of that experiment, LASCO (Large Angle Spectrographic Coronagraph), and is now in collaboration with Dr. Russell Howard and with other scientists at NRL. 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. Stephan Martin of Williams is the collaborating staff member. The experiment is funded by a grant from NASA’s Guest Investigator Program for the SOHO spacecraft.

An unusual aspect of Pasachoff’s experimental teams is that they include so many undergraduate students. For the 1999 eclipse, participants included Williams College students Kevin Russell ‘00, Sara Kate May ‘00, Rebecca Cover ‘00, Daniel Seaton ‘01, Joey Shapiro ‘01, Misa Cowee ‘01, Darik Velez ‘01, and Rossen Djagalov ‘02; Keck Northeast Astronomy Consortium Summer Fellow Alexandru Ene ‘02, a student from Romania who studied at Middlebury College and who is transferring to Harvard; and probable future Williams student Mark Kirby ‘02, from Deep Springs College in California near Dyer, Nevada. Recent Williams alumni Timothy McConnochie ‘98 and Christina Reynolds ‘97 will also participate. Scientific staff included Bryce Babcock of Williams College; Lee Hawkins of Wellesley College; Stephan Martin of Williams College; and Jonathan Kern, an optics designer at Caltech. Additional support came from the W.M. Keck Foundation; from the Massachusetts Space Grant, and from the Safford Fund, set up by his descendents in honor of the second director of the Hopkins Observatory, Truman Henry Safford.

Pasachoff was Carter Lecturer of the Carter Observatory, New Zealand, for 1998. His term ended as Retiring Chair of the Astronomy Division of the American Association for the Advancement of Science and he chaired and organized a session on the latest NASA results at the general meeting in Anaheim during January 1999. Pasachoff continues as President of the Williams College Chapter of Sigma Xi. He has become the book reviewer for physical science for the Key Reporter, the newsletter of Phi Beta Kappa.

While preparing for his 29^th solar eclipse, Pasachoff was busy not only on scientific tasks but also on educational tasks relevant to the safe observing of the eclipse by populations across the Americas, through his roles as Chair of the Working Group on Eclipses of the International Astronomical Union (IAU) and as Chair of the Subcommittee on Public Education through Eclipses of the Commission on the Teaching of Astronomy of the IAU.
(See http://www.williams.edu/Astronomy/eclipses/.)

Continuing their collaboration on the overlap of astronomy and art, Pasachoff and Prof. Roberta J.M. Olson participated in the September 1998 meeting of the Northeast American Society for Eighteenth-Century Studies by delivering papers. Pasachoff’s paper was on the lives and comet drawings of William and Caroline Herschel. William Herschel discovered the planet Uranus in 1781 and Caroline discovered numerous comets, eventually receiving the Gold Medal of the Royal Astronomical Society.

Kwitter and her colleagues are continuing their studies of planetary nebulae – glowing gas shells ejected by dying stars. (See http://oposite.stsci.edu/pubinfo/pr/97/pn/) The chemical composition of these extraordinarily beautiful and complex objects yields important clues as to the nature of the nuclear processing that went on inside the parent star. These stars, which make up the majority of those in our Milky Way Galaxy, have masses between about 0.8 and 10 times the mass of our Sun. In addition to the evolutionary history of their progenitors, planetary nebulae as a class offer an opportunity to study the properties of the surrounding interstellar medium and the chemical evolution of the Galaxy as a whole.

Kwitter and Dick Henry (U. Oklahoma) are finishing a new determination of carbon abundances in planetary nebulae. They have used newly recalibrated archived data from the International Ultraviolet Explorer satellite to study the production of carbon in stars that produce planetary nebulae. Jim Bates ‘98, and summer 1998 Keck exchange student Kelli Corrado (Colgate University ‘99) contributed to this project by analyzing spectra from planetary nebulae visible from the southern sky. Joel Iams ‘01 and Hugh Crowl (Wesleyan ‘00) accompanied Kwitter on an observing run at Kitt Peak National Observatory in June 1999.

Kwitter, Henry, and Bruce Balick (U. Washington) are working on a multi-faceted project to study planetary nebulae as individual objects and as probes of chemical evolution in the Galaxy (and possibly in other galaxies as well). In June 1999, they received a 3-year NSF grant for $237,000 in support of this project.

Kwitter continues her term on the Space Sciences panel of the National Research Council Associateship Programs Review. The NRC is the principle operating agency of the National Academy of Sciences and National Academy of Engineering, and awards postdoctoral and senior associateships at national facilities. With co-author Steven Souza, she has written three books of hands-on experiments for J. Weston Walch publishers. (See Faculty Publications)

Under the guidance of Steve Martin, the observatory continues to be used in support of the astronomy curriculum. Over 150 introductory astronomy students completed over 900 observations of celestial objects over the course of the academic year. These included observations, photographs, and CCD images of the sun, moon, and many nebulae and galaxies.

Martin participated in the Williams College Eclipse Expedition to Palm Beach, Aruba in February. He supervised an experiment carried out during the total solar eclipse 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). Seven excellent images of the corona were obtained during totality. This experiment was supported in part by the Committee for Research and Exploration of the National Geographic Society.

Martin continued his responsibilities for maintaining the World Wide Web pages for the Astronomy Department and, sponsored by Saunders College Publishing, for Pasachoff On-Line, a site devoted to Pasachoff’s introductory astronomy textbook, Astronomy: From the Earth to the Universe. Martin also developed web pages for each of the introductory astronomy courses. These pages contain links to useful astronomy sites and provide a forum for students to display images that they have taken with the observatory’s CCD system and photographic cameras as part of their observing projects. Carlett Malcolm ‘01 worked on design aspects of web pages. (www.williams.edu/astronomy). There are also pages dedicated to observations made by the Williams College eclipse teams at the total solar eclipses in Aruba and Romania.

Laura Brenneman ‘99 continued her 1998 summer research on spiral galaxies for a senior thesis. Her work with Paul Goudfrooij of the Space Telescope Science Institute continued through the year. They examined globular cluster populations in galaxy halos. Pasachoff was her on-campus thesis advisor.

Student roof TA’s, responsible for operating the telescopes, participating in the research projects, and assisting introductory students with assignments, included Laura Brenneman ‘99, Rebecca Cover ‘00, Robert Lyman ‘99, Daniel Seaton ‘01, Joey Shapiro ‘01, Jason Slingerlend ‘00, Christopher Spence ‘00, Mithandra Stockley ‘01, Rossen Djagalov ‘02, and Johanna Heinrichs ‘02.

The Milham Planetarium was run by Kevin Russell ‘00, Sara Kate May ‘00, Erik Klemetti ‘99, Daniel Seaton ‘01, Darik Velez ‘01, and Bethany Cobb ‘02. The fall show was “The Beauty of Mars.” In the spring semester, Russell wrote a new show: “A Total Solar Eclipse!” Summer shows were given by the summer research students. The Planetarium is supported in part by the Brandi fund.

During the summer of 1999, the following Keck exchange students were in residence at Williams: Hugh Crowl (Wesleyan ‘00) working with Karen Kwitter and Alexandru Ene (Middlebury ‘02) working with Jay Pasachoff. Williams students working on research in the summer of 1999 were Joel Iams ‘01, working with Karen Kwitter, Kevin Russell ‘00 and Sara Kate May ‘00 working with Jay Pasachoff, and Misa Cowee ‘01 working with Steve Martin. Rebecca Cover ‘00 worked at the Harvard-Smithsonian Center for Astrophysics on a joint project between Pasachoff and Nancy Evans of the CfA. Joey Shapiro ‘01 worked at the Imaging Processing and Analysis Center (IPAC) of Caltech on infrared data. Dan Seaton ‘01 worked at the Haverford astronomy department as part of the Keck exchange. Duane Lee ‘99 worked at the Wesleyan astronomy department as part of the Keck exchange. Matt Silver is working in Australia on junior-year abroad with Lawrence Cram, Mills Professor of Astronomy at the University of Sidney. Feng Zhu ‘02 worked on various astronomy web sites as an office of Information Technology Mellon Fellow. Darik Velez ‘01 did library work on eclipse experiments as part of the Mellon Minority Undergraduate Fellowship Program.

ASTRONOMY DEPARTMENT AND THE HOPKINS OBSERVATORY

ASTRONOMY COLLOQUIA

OFF-CAMPUS ASTRONOMY COLLOQUIA AND LECTURES

POSTGRADUATE PLANS OF ASTROPHYSICS MAJORS