ASTRONOMY DEPARTMENT AND THE HOPKINS OBSERVATORY

Faculty this year included Karen B. Kwitter, Ebenezer Fitch Professor of Astronomy and Chair; Jay M. Pasachoff, Field Memorial Professor of Astronomy and Director of the Hopkins Observatory; and Steven P. Souza, Instructor in Astronomy and Observatory Supervisor.

The Department graduated nine astrophysics majors in 2004: Paul Crittenden, Jesse Dill, Robertson Follansbee, Matthew Hoffman, Martin Mudd, Lissa Ong, Davis Stevenson, David Ticehurst and Galen Thorp; Sarah Croft was an astronomy major. Incoming senior astrophysics majors are Ryan Carollo, Zophia Edwards, Kamen Kozarev, and Terry-Ann Suer. Incoming juniors are David Butts, Joseph Gangestad and Owen Westbrook. Alan Cordova and Yariv Pierce are astronomy majors.

Kwitter’s research centers on the late stages of stellar evolution of the most common kinds of stars: those of medium mass between about 0.1 and 8 times the mass of the sun. Specifically, she studies the chemical composition of planetary nebulae, the cast-off outermost layers of these stars near the end of their lifetime. Spectra reveal their chemical compositions, which may be affected by the nuclear processes that went on previously inside the parent star. Along with colleague Richard Henry of the University of Oklahoma, she has detailed the behavior of sulfur, chlorine and argon; elements that are not expected to be affected by nuclear processing in the nebulae’s parent stars, and therefore serve as markers for the composition of the original stellar material. In collaboration with Jacquelynne Milingo, now of Franklin & Marshall College, Kwitter and Henry have obtained data at Kitt Peak National Observatory and at Cerro Tololo Inter-American Observatory to examine a class of planetary nebulae that come from the more massive precursors of planetary nebulae. Their goal is to examine the abundances of nitrogen and oxygen to search for evidence that fusion near the bottom of the star’s convective envelope has resulted in the conversion of some of the oxygen into nitrogen. Davis Stevenson ’04 accompanied Dr. Steven Souza and Milingo to Kitt Peak in July 2003 and to Cerro Tololo in November 2003.

Last year, Kwitter, Reginald Dufour of Rice University and Richard Henry were awarded time on the Hubble Space Telescope to investigate the behavior of emission from ionized carbon atoms in planetary nebulae and other ionized hydrogen regions. Carbon, an element critical to life, is also an important constituent of interstellar clouds. It is notoriously difficult to measure the abundance of carbon in gas clouds from observations in the visible part of the spectrum; therefore observations in the ultraviolet are required, hence this Hubble Space Telescope project.

During the summer of 2003, Lissa Ong ’04, Davis Stevenson ’04, and KNAC Summer Fellow Megan Roscioli (Haverford ’05) worked with Kwitter on various projects relating to spectroscopic analyses of planetary nebulae. These included reduction and analysis of spectra obtained at Kitt Peak National Observatory and at Cerro Tololo Inter-American Observatory. Stevenson continued her research with Kwitter as a senior honors thesis. For more information about KNAC, see http://www.wellesley.edu/Astronomy/keck/.

In the summer of 2004, Joseph Gangestad ’06 worked with Kwitter to study archival ultraviolet observations of a sample of planetary nebulae taken with the now-defunct International Ultraviolet Explorer satellite, in order to help analyze more recent observations of the same objects with the improved capabilities of the Hubble Space Telescope.

Kwitter and Henry’s web-based Gallery of Planetary Nebula Spectra continues to be successful. The gallery is a database that incorporates a graphical package to display spectra. It contains high-quality spectroscopic data on 88 planetary nebulae. The website was designed with the help of several Williams Instructional Technology students in the summer of 2002. Kwitter developed two exercises, which are included on the website (cf.williams.edu/public/nebulae/) to explicate the data and to illustrate basic concepts of atomic physics and radiation. The site has thus far received more than 2500 hits.

Kwitter continued on the Observatories Council of the Associated Universities for Research in Astronomy, Inc. (AURA), notably as the only representative from a liberal arts college. The function of the Observatories Council is to advise AURA on the management and future direction of the National Optical Astronomy Observatories (NOAO), which includes Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory and the NOAO Gemini Science Center. Kwitter has also continued as a member of the Space Sciences panel reviewing applications for the Associateship Programs Review conducted thrice yearly by the National Research Council, the principal operating agency of the National Academy of Sciences. The NRC panels vets applications for postdoctoral research appointments at nationally funded laboratories and centers. Kwitter also continues on the advisory boards of Annual Editions: Astronomy, and the Encyclopedia of Astronomy and Astrophysics.

Pasachoff was very involved this year in a extremely rare event, the June 8, 2004, transit of Venus across the face of the sun. This event was the first transit of Venus since the year 1882. Only five transits of Venus have been observed in all history: in 1639, 1761, 1769, 1874, and 1882. Pasachoff’s earlier work on a transit of Mercury, in collaboration with Glenn Schneider of the Steward Observatory, University of Arizona, and Leon Golub of the Harvard-Smithsonian Center for Astrophysics, appeared in Icarus. They analyzed observations of the Mercury transit to explain the black-drop effect, the ligature that links the silhouette of the planet with the background sky outside the solar limb, making timing of the contacts uncertain. Transits of Venus are historically very important, since, for hundreds of years, timing transits of Venus have used a method of Halley to determine the distance to Venus and thus the whole scale of the solar system. They also play a new role in providing close-up transit observations that can help us better understand the transits of extra solar planets across their stars’ surfaces, as are being increasingly observed.

Pasachoff and Bryce Babcock, Staff Physicist and Coordinator of Science Facilities, carried out a successful transit expedition to Thessaloniki, Greece, where they enjoyed the hospitality of Prof. John Seiradakis at the Aristotelian University of Thessaloniki. Participants included David Butts ’06, Joseph Gangestad ’06, Owen Westbrook ’06, Alan Cordova ’06, Keck Northeast Astronomy Consortium Bryn Mawr student Kayla Gaydosh ’05, and Rob Wittenmyer ’98 (recent San Diego State University M.A. in Astronomy, just beginning a Ph.D. astrophysics program at the University of Texas). Their work was sponsored by a grant Pasachoff received from the Committee for Research and Exploration of the National Geographic Society. They were joined in Greece by Glenn Schneider. Simultaneously, Steven Souza, Observatory Supervisor, observed the transit from Williamstown using the Observatory’s solar telescope for the portion the transit that was visible there. Gangestad received a grant from Sigma Xi for his participation.

Schneider and Pasachoff continued their work on observations of transits with NASA’s Transition Region and Coronal Observer (TRACE). They, aided by Gaydosh, are reducing TRACE observations of the transit. Results appear at the Williams College transit website at http://www.williams.edu/astronomy/eclipse/transits/index.html. Venus’s atmosphere can be seen clearly, and the evolution of its visibility can be followed. Pasachoff and Schneider also worked with Richard Willson of Columbia University on Willson’s observations of the effect of the transit on the total solar irradiance, formerly known as the solar constant, with NASA’s ACRIMSAT. The 0.1% dip caused by the geometrical blocking of the solar disk by Venus, and effects of solar limb darkening, can be followed.

Pasachoff had used TRACE earlier along with an experiment, SUMER, on the Solar and Heliospheric Observatory, and ground-based observing at the Swedish Solar Telescope at the Roque de los Muchachos Observatory on La Palma, Canary Islands, Spain, to observe the solar chromosphere at high resolution in order to study the fine structure in it known as spicules. Butts and Gangestad joined Pasachoff in La Palma for the observing run, where they worked with Bart De Pontieu of the Lockheed Martin Solar Astrophysics Laboratory, who provided their Solar Optical Universal Polarimeter (SOUP) filter. Butts and Kamen Kozarev ’05, who will continue on this topic for his senior thesis, worked during the summer on reduction of these data, including a working visit to De Pontieu in Palo Alto to set up suitable computer programs in the IDL system. The chromospheric work is supported by a new 3-year grant Pasachoff received from NASA as part of the Guest Investigators support program for TRACE. The work is also in collaboration with Daniel Seaton ’01, now a graduate student in solar astronomy at the University of New Hampshire, with Leon Golub and Edward DeLuca of the Harvard-Smithsonian Center for Astrophysics, who built and help run the TRACE spacecraft, and with Klaus Wilhelm, former head of the SUMER project.

Pasachoff, Babcock, and Souza continued their joint work with James Elliot’s group at MIT to study occultations of stars by Pluto and other outer-solar-system objects. David Ticehurst ’04 completed his senior thesis on the observations of an occultation by Pluto that had given important results on the increasing pressure of Pluto’s atmosphere. Pasachoff, Babcock, Souza, and Ticehurst, along with MIT and other colleagues, submitted a detailed paper to the Astronomical Journal about the results of their optical observations using the 2.2-m reflector of the University of Hawaii at its Mauna Kea Observatory, as well as observations from the Air Force’s 3.5-m telescope on Maui. The Williams and MIT groups received a joint equipment grant from NASA to purchase four electronic-camera systems, two for Williams and two for MIT, for future occultation work. The occultations, when these objects pass in front of distant stars, reveal the atmospheres of the occulting objects and the conditions in them. Observations are planned for the atmospheres of Pluto, Neptune’s moon Triton, and Kuiper-belt objects. Souza and Babcock have been particularly active in specifying the equipment to be purchased and testing possibilities.

Pasachoff and Donald Lubowich of the American Institute of Physics and Hofstra University continued their collaboration on studying interstellar deuterium. All the deuterium in the universe was formed in the first 1000 seconds after the big bang, so determining the deuterium abundance and distribution has important consequences for cosmology. In April 2004, Pasachoff joined their collaborator Jayaram Chengalur of the Tata Institute for Fundamental Research at their Giant Metrewave Radio Telescope outside Pune, India, to try to detect the fundamental spectral line of deuterium at a radio wavelength of 92 cm, which is a frequency of 327 MHz. They observed in the directions of two galactic clouds that are known to have a relatively high abundance of other light isotopes. Terry-Ann Suer ’05 and KNAC summer fellow Peter Forshay (Haverford ’05) worked on prior deuterium results during the summer of 2003, studying optical attempts of detecting interstellar deuterium in the direction of nearby stars.

Pasachoff observed the total solar eclipse of November 23, 2003, from a Boeing 747-400 over Antarctica. With Glenn Schneider aboard the flight, they observed the solar corona with a Santa Barbara Instrument Group (SBIG) electronic camera and other cameras. Data reduction has begun; an early stage can be seen at http://www.williams.edu/astronomy/eclipse. Subsequently, Pasachoff observed the partial solar eclipse of April 19, 2004, from Cape Town, South Africa.

Pasachoff is part of a consortium headed by Nancy Evans of the Harvard-Smithsonian Center for Astrophysics that has received time for Cycle Six of the Chandra X-ray Observatory. They will be observing x-rays from the double star cluster h and chi Persei. The work is related to a past thesis on optical observations of h and chi Persei by Rebecca Cover ’00.

Pasachoff continued his collaboration with Roberta J. M. Olson of the New-York Historical Society on studying the relation of art history and astronomy. At the meeting of the College Art Association in Seattle in April, they gave a paper on the roles of Galileo and others in the Medici court in a symposium related to the role of courts.

Pasachoff was awarded the 2003 Education Prize of the American Astronomical Society at the January 2004 meeting in Atlanta. In addition, Pasachoff organized a session on public education using NASA’s Great Observatories: Hubble, Chandra, and Spitzer.

Pasachoff was elected President of Commission 46 on Education and Development of the International Astronomical Union at its triennial General Assembly in Sydney, Australia. He continues as the United States National Liaison to the Commission as well as Chair of the Working Group on Solar Eclipses.

Pasachoff participated in a Special Session on “Effective Teaching and Learning of Astronomy” at the General Assembly. He joins John Percy of the University of Toronto as editor of the proceedings, which have been submitted on contract to Cambridge University Press.

Pasachoff continues on the science board of the World Book and as consulting editor for astronomy of the McGraw-Hill Scientific Encyclopedia and Yearbooks. He is on the Council of Advisors of the Astronomy Education Review electronic journal. See http://aer.noao.edu/. Pasachoff continues as science book reviewer for The Key Reporter, the Phi Beta Kappa newsletter. He continues as advisor to the children’s magazine Odyssey.

Pasachoff worked with Milos Mladenovic of the Williams College Center for Information Technology to post regular updates and press releases on a wide variety of astronomical topics on the Web at www.solarcorona.net, at www.eclipses.info, and at www.transitofvenus.info.

Dr. Steven Souza directs the department’s observing program and facilities, which offer varied nighttime and solar observing experiences for introductory and advanced students. This year he hosted numerous visiting individuals and groups, including Friday night planetarium groups, alumni, Center for Development Economics students, visiting classes from local schools, Family Weekend attendees, and student previews and prospective students. He hosted many nights of observing of the Mars opposition (close approach to Earth) of summer 2003, the spectacular aurora of October 2003 (http://www.williams.edu/Astronomy/aurora10302003_gallery/index.html), and the lunar eclipse of November 2003. He supervises ten observing teaching assistants, and trains them in the use of our observatory facilities. Souza teaches all laboratory sections in the department. He continues the process of revising or replacing many of the existing laboratory exercises using new software, web resources, and data.

Souza continues to maintain and improve the Observatory’s instrumentation and facilities. He acts as liaison between the Department and the Buildings and Grounds Department on physical plant issues, including campus lighting. Improvements made last year enabled this year’s students in Kwitter’s Observation and Data Reduction Techniques in Astronomy (ASTR 211) to successfully complete a variety of imaging, spectroscopy, and radio observation projects. He developed a system to deliver dry air to the VersArray CCD to mitigate condensation problems, and developed a simplified procedure for imaging using the VersArray CCD in the introductory class. The results of these efforts can be seen at http://www.williams.edu/astronomy/hopkins/CCD_S04.html.

During the summer of 2003, Ryan Carollo ’05 worked with Souza on the continuing renovation of the Carroll-spar solar telescope, and Galen Thorp ’04 did preliminary work aimed at understanding the effects of atmospheric “seeing” on the Observatory’s 0.6-m reflector. Souza advised Thorp on equipment issues in the course of his senior thesis with Pasachoff.

Souza participated in many observations and astronomical events in 2003–04. He traveled to Kitt Peak National Observatory in Arizona in June 2003, and to Cerro Tololo Inter-American Observatory in Chile in November 2003, to work with Dr. Jacqueline Milingo, a collaborator of Kwitter at Franklin & Marshall College, on spectroscopy of planetary nebulae. He prepared for and, with Pasachoff and Dr. Bryce Babcock, attempted to observe the occultation of a star by Titan in November 2003. He prepared the Williams College imaging experiment for the November 2003 total solar eclipse viewed by Pasachoff from a Qantas 747 over Antarctica. In February 2004, Souza worked with Mark Weber, Mike Harris, and Dr. Leon Golub of the Smithsonian Astrophysical Observatory to calibrate a telescope destined to fly on the SOLAR-B spacecraft by making observations of the Sun with the instrument mounted piggyback on the Hopkins Observatory 0.6-m telescope. Souza and Babcock prepared the experiments brought to Thessaloniki, Greece by the Williams College contingent to observe the June 2004 transit of Venus. He also prepared and conducted an observation of this event here at Williams, using the Carroll solar telescope and a CCD camera. Although no Pluto observations were undertaken this year, Souza worked with Pasachoff, Babcock, and the occultation team at MIT headed by Dr. James Elliot to develop a NASA equipment grant proposal for future occultation observations, which has been approved.

Souza has standardized the department on Mac OS X for Mac and UNIX applications (retiring Linux machines), and Windows 2000 for PCs. He set up networks of Mac OS X workstations for IRAF and IDL, software packages commonly used in astronomical research. He acts as liaison between the department and OIT, and represents astronomy in thrice yearly “Sci-Tech” meetings. He maintains the Astronomy Department website, and provided guidance to summer 2003 WIT students updating and reorganizing the Eclipse portion of the website. New pages were added for the 2003 total eclipse over Antarctica, a 2004 partial eclipse in South Africa, and upcoming eclipses over Africa and the Pacific.

During the year, the Hopkins Observatory presented planetarium shows on Friday evenings entitled “The Latest Astronomy from Space.” Shows were designed and given by students Jesse Dill ’04, Davy Stevenson ’04, Sarah Croft ’04 and Ryan Carollo ’05 with Jay M. Pasachoff.

Kwitter, Pasachoff, and Souza attended the KNAC Student Symposium at Wellesley College in October 2003.

David Ticehurst ’04 received the Milham Prize in Astronomy, was elected a member of Phi Beta Kappa and graduated magna cum laude with honors in Astrophysics.