Faculty of the Astronomy Department included Jay M. Pasachoff, Field Memorial Professor of Astronomy, Chair, and Director of the Hopkins Observatory; Karen B. Kwitter, Ebenezer Fitch Professor of Astronomy; and Steven P. Souza, Instructor in Astronomy and Observatory Supervisor. Bryce A. Babcock, retired as Staff Physicist and Coordinator of Science Facilities, is Associate of the Hopkins Observatory. Marcos Peñaloza-Murillo, Professor of Physics at the Universidad de los Andes in Mérida, Venezuela, arrived for the calendar year as a Fulbright Scholar.
Jay Pasachoff devoted a major effort this year to the June 5 transit of Venus across the face of the Sun, the second of the twenty-first century pair and only the sixth such transit ever observed (1639, 1761/1769, 1874/1882, and 2004) and the last to be seen before the year 2117, 105.5 years in the future. The scientific efforts were devoted both to using the transit in liaison with a spacecraft in orbit around Venus to study Venus’s atmosphere and to observing the transit in our solar system in detail as an analogue to the thousands of exoplanet transits that are now being observed by the Kepler spacecraft and otherwise. In addition to preparing for the scientific observations from a wide variety of observatories around the world and in space, Pasachoff arranged public outreach to alert the general public of the significance of and interest in the transit of Venus. He had a “Comment” in Nature before the transit and an Op-Ed piece in The New York Times on the morning of the transit, as well as an Academic Minute for radio and for the web.
Pasachoff was joined by Babcock, student Muzhou Lu ’13, colleague Glenn Schneider from the University of Arizona, and others at the Mees Solar Observatory of the University of Hawaii at the 10,000-foot altitude of Haleakala, Maui, for the observations on the day of the transit. They collaborated in a Venus Twilight Experiment, which sent 9 coronagraphs to observe Venus’s atmosphere from a variety of sites around the world, elaborating on the observations that Pasachoff and Schneider had made for the 2004 transit with NASA’s Transition Region and Coronal Explorer spacecraft. Thomas Widemann of l’Observatoire de Paris à Meudon and Paolo Tanga at the l’Observatoire de Côte d’Azur in Nice related the transit observations to Venus Express spacecraft observations of the Cytherean atmosphere’s circulation. In collaboration with Ron Dantowitz of the Dexter and Southworth Schools, Brookline, MA, and with Aram Friedman of Ansible Technologies, Princeton, NJ, they amassed a wide variety of observations from Haleakala; an animation made by Friedman appears at http://www.youtube.com/ansibletech. Ron Lucas of the University of Sydney; Eric Pilger ’82 of the Hawaii Institute of Geophysics, University of Hawaii; and Joel Moskowitz of New York participated on site, where their work was facilitated by Rob Rakowski of the Haleakala Amateur Astronomers. Pasachoff, Babcock, and colleagues also worked with Jeff Kuhn, Stuart Jefferies, and Garry Nitta of the Mees Solar Observatory faculty and staff on arranging observations. Pasachoff’s expedition to Haleakala was sponsored in part by a grant from the Committee for Research and Exploration of the National Geographic Society.
Pasachoff had obtained commitments of telescope time not only at Haleakala, but also at Sacramento Peak Observatory, New Mexico (where the IBIS imaging spectrograph at the Dunn Solar Telescope, equivalent to a 55,000-mm telephoto, was operated by Kevin Reardon ’92, who is joining the National Solar Observatory staff), at Kitt Peak, Arizona, and at the Big Bear Solar Observatory, California, and with spacecraft including NASA’s Solar Dynamics Observatory, the Solar Optical Telescope (an American telescope run by Lockheed Martin Solar and Astrophysics Laboratory, where Emma Lehman ’10 had been on the staff) on the Japanese Hinode spacecraft, and NASA’s ACRIMSAT (Active Cavity Radiometer Irradiance Measurement satellite) and SORCE/TIM (SOlar Radiation and Climate Experiment/Total Irradiance Measurement). Two days after the transit, Pasachoff reported on preliminary results at a public lecture sponsored by the Keck Observatory on the Big Island of Hawaii. The following Monday, Pasachoff gave an invited lecture that included preliminary results at the 220th meeting of the American Astronomical Society in Anchorage, Alaska. He subsequently prepared the 365daysofastronomy.org summary of the transit and the Sky & Telescope article about the observations as well as a McGraw-Hill Yearbook entry on the 2012 transit.
Pasachoff and William Sheehan, a historian of science of Minnesota, analyzed early reports of the discovery of the transit of Venus, comparing them with what we now know Venus’s atmosphere looks like during a transit based on the 2004 observations. They showed that Mikhail Lomonosov, the important Russian scientist who is almost always credited with the discovery of the Cytherean atmosphere, did not, in fact, detect the atmosphere, undoubtedly confusing artifacts for the atmosphere that he had expected on religious, plurality-of-worlds grounds. Their report was published in the Journal for the History and Heritage of Astronomy, where it has been widely discussed.
Pasachoff and Babcock collaborated on several projects that each involved student participation in expedition research, an interesting scientific question, and Federal grant support:
At the October 2011 meeting of the Division of Planetary Sciences of the American Astronomical Society held in Nantes, France, Pasachoff, Babcock, and Souza participated with MIT colleagues in the report of observations of the occultation of a star by Pluto in May 2011 with the 0.6-m DFM telescope on the roof of the Thompson Physics and Astronomy Laboratory. On May 22, 2011, Souza had used the on-campus 0.6-m telescope with a POETS (Portable Occultation, Eclipse, and Transit System), one of three that Williams College has through a NASA equipment grant, to successfully observe an occultation of a star by Pluto, showing a diminution of the total intensity of the star + Pluto by about 20% for about 100 seconds. Also present for the observations were Pasachoff, Babcock, Matt Hosek ’12 and Shubhanga Pandey ’13. The results were used to refine the model of Pluto’s and Charon’s orbits and to improve the predictions of the observations from two telescopes on Oahu in Hawaii of the June 22/23, 2011, occultation of both Pluto and Charon and the June 26/27 occultation of Pluto with an additional occultation by its moon Hydra, also reported upon at the Nantes meeting. Pasachoff, Babcock, Pandey, and the Keck Northeast Astronomy Consortium Summer Fellow, David Amrhein ’13 from Wesleyan, observed with telescopes at Oahu’s Windward and Leeward Community College observatories. Simultaneously, colleague Michael Person from MIT observed from SOFIA (Stratospheric Observatory for Infrared Astronomy), an instrumented NASA airplane with a 2.4-m telescope and colleague Amanda Gulbis from the South Africa Astronomical Observatory observed from Mauna Kea. The work is supported by a research grant from NASA Planetary Astronomy. In May 2012, a new 3-year NASA Planetary Astronomy grant was received by Pasachoff for continuing the stellar occultation work, especially in view of the flyby of Pluto by NASA’s New Horizons spacecraft in July 2015. See http://www.stellaroccultations.info to gather links to the various work the Williams faculty and students have carried out to study the outer solar system through observing those objects occulting distant stars.
Already having published the results of the total solar eclipse observations made in Easter Island at the total solar eclipse in 2010, in collaboration with Muzhou Lu ’13, Pasachoff went on to write up and publish the scientific results from the earlier 2009 eclipse in China, at which the weather had not been as favorable. The results include a comparison with observations made from the Williams College site at Tianhuangping, China, and a site on Enewetok atoll in the Pacific Ocean. They worked with Hana Druckmüllerová of the Brno University of Technology, Czech Republic, and Vojtech Rusin and Metod Saniga of the Astronomical Institute in Tatranská Lomnica, Slovakia, as co-authors of the paper for the Astrophysical Journal.. They compared the ground-based observations with space observations from NASA’s Solar Dynamics Observatory, the European Space Agency’s PRoject for Onboard Autonomy (PROBA2), ESA’s and NASA’s Solar and Heliospheric Observatory, and NASA’s (Solar Terrestrial Relations Observatory (STEREO).
Pasachoff worked with John Seiradakis and Aris Voulgaris of the Aristotle University of Thessaloniki, Greece, on papers for Solar Physics about chromospheric and coronal spectra taken at the total eclipses, including the Easter Island eclipse. Paul Gaintatzis an Thanasis Economou were coauthors. The spectra show the decline in overall coronal temperature with the sunspot cycle, and provide a new way of determining the length of totality and of the flash spectrum through such spectral observations.
Pasachoff continued work on the interstellar medium, especially through considerations of the cosmic deuterium abundance. He works in collaboration with Donald Lubowich of Hofstra University.
Pasachoff observed the partial solar eclipse of November 25, 2011, from Invercargill, New Zealand. It was his 54th solar eclipse.
Pasachoff took 8 students to observe the annular solar eclipse of May 20, 2012, from the western United States, where the end of the annular eclipse was visible. Seven of the students had been in his Solar Physics course, Astronomy 412, and the other was the exchange student Eric Edelman (Wesleyan ’13), the Keck Northeast Astronomy Consortium Summer Fellow. He used his new grant from the Solar Research Program of the Atmospheric and Geospace Sciences Division of the National Science Foundation for studies the two central solar eclipses of 2012. Pasachoff worked with Tom Kuiper of NASA’s Jet Propulsion Laboratory for use of JPL’s 34-m radio telescope at Goldstone; and with Dale Gary of the New Jersey Institute of Technology and Tim Bastian of the National Radio Astronomy Observatory in planning and making radio-telescope observations of the May 20 annular solar eclipse with the Jansky Very Large Array near Socorro, New Mexico. Additional support for student participation was received from the Massachusetts Space Grant Consortium, sponsored by NASA. The event was Pasachoff’s 55th solar eclipse.
Pasachoff and colleagues planned for detailed observations of the November 14, 2012, total solar eclipse from Port Douglas, Newell, and Cairns in Queensland, Australia, again supported by the National Science Foundation grant. Babcock, Lu ’13, and Lucas will be among those participating.
Pasachoff, Kwitter, and Souza all attended the Keck Northeast Astronomy Consortium (KNAC) Faculty Meeting at Haverford College in July 2011, and the KNAC Student Symposium at Wellesley College in September 2011.
Peñaloza-Murillo had participated in two previous total solar eclipse observations with Pasachoff, in 2001 in Zambia and in 2009 in China. As an atmospheric physicist, he is interested in the response of the Earth’s atmosphere to the cooling that takes place when the Moon blocks the incoming sunlight. He worked with Teddy Amdur ’15 during the spring and summer of 2012 on the project. He sent measuring instruments with Markus Gonzales ’13 to the Jansky Very Large Array as part of the Williams College observations of the May 20 annular eclipse.
Karen Kwitter continued her research into the chemical composition of planetary nebulae (PNe). These ejected shells of dying sun-like stars contain products of nuclear processing– helium, nitrogen, carbon – inside their parent stars, and so are valuable probes into the chemical enrichment history of the Milky Way and other galaxies. Kwitter’s research concentrates on PNe in the Milky Way and in the neighboring Andromeda Galaxy (M31), 2.5 million light-years away, and a near twin.
In the summer of 2011 Kwitter supervised three students: Matt Hosek ‘12, Aven King ‘12, and Alice Sady ‘13. These students learned to use CLOUDY (Ferland et al. 1998) to create computer models of planetary nebulae in M31, the Andromeda Galaxy, that yield information about the exciting stars at their centers. Their work is acknowledged in a paper published in July 2012 in the Astrophysical Journal.
Kwitter and colleagues Dick Henry (U. Oklahoma) and Bruce Balick (U. Washington) (KHB) are continuing their collaborative research on PNe in M31. The spectra they obtained of 16 M31 planetary nebulae (taken with Emma Lehman ’10 at the 8.1-meter Gemini-North telescope on Mauna Kea) were part of the input for the models that Matt, Aven and Alice worked on. KHB have applied for additional time in Fall 2012 with Gemini-North to observe ten more planetary nebulae in M31, which would help in defining M31’s oxygen gradient (the rate at which the oxygen abundance declines with distance from the center of the galaxy).
KHB and a group of colleagues were awarded time with the Hubble Space Telescope to observe Milky Way PNe in the ultraviolet part of the spectrum to detect bright emission lines from the element carbon, which emits only feebly in the optical region. The ratios of carbon to nitrogen and to oxygen form important constraints on the evolution and nucleosynthesis inside PN parent stars.
With colleagues from U. Texas, Rice, U. Oklahoma and U. Kansas, Kwitter is participating in a project using the VIRUS-P integral-field spectrograph on the 2.7-m telescope at McDonald Observatory in west Texas. Matt Hosek ’12 analyzed VIRUS-P spectra of the Eskimo Nebula, NGC 2392, for his senior honors thesis, discovering evidence for variable dust extinction across the face of the nebula. He and Kwitter traveled to McDonald in April 2012 to take further observations.
In July 2011, Kwitter gave the invited talk on chemical abundances at International Astronomical Union Symposium #283 in Tenerife, Canary Islands, “Planetary Nebulae – An Eye to the Future.” Her talk was entitled “Reuse, Reduce, Recycle: Planetary Nebulae as Green Galactic Citizens.” At the Symposium, Kwitter was elected to the IAU’s Working Group on Planetary Nebulae. In September, Kwitter attended the KNAC Student Research Symposium at Wellesley College.
Souza conducts and supervises the astronomy observing program, and all indoor labs and daytime observing. He hosted numerous observatory visitors, including planetarium groups, student previews and prospectives, and groups from the American Museum of Natural History, the Williams College Summer Science Program, and the Massachusetts Teachers Association.
On June 5, 2012, Souza organized on-campus viewing of the transit of Venus at our TPL rooftop observatory, assisted by Joe Iafrate ’14, and K. Kwitter. Using solar-filter cardboard glasses and 3 telescopes outfitted with safe-viewing filters, more than 50 visitors patiently waited out the clouds to catch the rare sight of Venus in front of the Sun.
Steven Souza continues to maintain and improve the observatory. With students Allen Davis ’14 and Yaron Teich, Vassar ’13, he cleaned and recollimated the 0.6-m telescope main mirror. He implemented a telescope/camera system for planetary imaging, and with help from Larry George and Michael Taylor he automated one of the small domes to complete a remotely-operated widefield imaging system. He upgraded all observatory and lab PCs and Macs, acted as department liaison with OIT and Facilities, and served as a first-year advisor and as a member of the Information Technology Committee.
Souza attended the Keck Northeast Astronomy Consortium (KNAC) Faculty Meeting in July 2011, and the KNAC Student Symposium in September 2011. He also attended a symposium honoring Prof. Michal Simon at Stonybrook University in June 2011, at which he presented a talk entitled “Interstellar C2, the Meatball, and the Purple Cow.”
Souza’s research effort to monitor variations in H-alpha emission in massive stars in open clusters continued. In the summer of 2011, with Allen Davis ’14 and Yaron Teich (Vassar ’13; Keck Northeast Astronomy Consortium exchange student) worked to improve the data reduction process and analyze the data for two clusters. Souza received a $4600 grant from the American Astronomical Society for new optical filters for the project, and presented a Science Lunch talk on his work.
Pasachoff continued as Chair of the Working Group on Eclipses of the International Astronomical Union’s solar commissions and as a member of the Johannes Kepler Working Group of the History of Astronomy commission. He was Vice-Chair (2011-2013) and Chair-Elect (2013-2015) of the Historical Astronomy Division of the American Astronomical Society. He continues as U.S. National Liaison to Commission 46 on Education and Development of the International Astronomical Union, of which he is a past president. He is also head of the Program Group on Public Education at the Times of Eclipses and Transits of the Commission on Education and Development. See http://www.eclipses.info and http://www.transitofvenus.info. Pasachoff continues as representative of the American Astronomical Society to the American Association for the Advancement of Science’s Astronomy Division, of which he was twice chair.
In July Pasachoff attended the KNAC Faculty Meeting at Haverford. In January, he attended the 219th meeting of the American Astronomical Society in Austin and in June, he attended the 220th meeting in Anchorage, Alaska. He attended the AAS’s Division of Planetary Sciences meeting in October in Nantes, France, and the Solar Physics Division’s meeting that was joint with the main AAS meeting in Anchorage, presenting papers at each.
Pasachoff continued his K-12 education work with PROM/SE (Promoting rigorous outcomes in K-12 mathematics and science education), an NSF-funded organization based at Michigan State University. He attended their final meeting in Washington, DC. (www.promse.msu.edu)
Pasachoff continued as President of Williams College’s Sigma Xi chapter and as the Williams representative to the NASA-sponsored Massachusetts Space Grant.
Pasachoff continues as astronomy consultant for the McGraw-Hill Encyclopedia of Science and Technology and its yearbooks. He also continues on the Physical Science Board of World Book. 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, a Fellow of the Society for Skeptical Inquiry, is on the editorial board of the Skeptical Inquirer. In a related course at Williams, he will again gave his seminar on Science, Pseudoscience, and the Two Cultures in spring 2013.
One of Pasachoff’s eclipse images, with data taken in conjunction with Muzhou Lu ’13 and Craig Malamut ’13 (Wesleyan) and processed by Hana Druckmüllerová, appears in a photography exhibit, Starstruck, at Bates College; it opened in June 2012.
Class of 1960 Scholars in Astronomy
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Matthew W. Hosek |
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DEPARTMENT COLLOQUIA
[Colloquia are held jointly with the Physics Department. See Physics section for listings.]
OFF-CAMPUS COLLOQUIA
Karen B. Kwitter
“Reuse, Reduce, Recycle – Planetary Nebulae as Green Galactic Citizens”
Invited talk at IAU Symposium #283
“Planetary Nebulae: An Eye to the Future”
Tenerife, Canary Islands
July 2011
Jay M. Pasachoff
“Transits of Venus and Mercury: Exoplanet Analogs in Our Solar System”
220th American Astronomical Society meeting
Anchorage, Alaska
May 2012
Jay M. Pasachoff
Keck Observatory
June 2012
Jay M. Pasachoff
“Transits of Venus in Public Education and Contemporary Research”
AAS Division of Planetary Sciences meeting
#EPSC-DPS2011-1773
Online video at http://transitofvenus.nl/wp/2011/10/16/four-giants-talk-about-transits/
October 2011
Pasachoff, Jay M., Steven P. Souza, Bryce A. Babcock, Shubhanga Pandey, Matthew W. Hosek, Michael J. Person, Amanda A.S. Gulbis, Amanda S. Bosh, Carlos A. Zuluaga, Eileen V. Ryan, an dWilliam H. Ryan
“The 22 May 2011 Pluto Occultaiton-Observed”
AAS Division of Planetary Sciences meeting
#EPSC-DPS2022-1784
Nantes
October 2011
Pasachoff, J. M., B. A. Babcock, S. Pandey, D. Amrhein, M. J. Person, A. A. S. Gulbis, A. S. Bosh, C. A. Zuluaga, S. Sallum, D. J. Tholen, R. Lucas, M. Kakkala, J. Ciotti, S. Plunkett, N. Hiraoka, W. Best, E. J. Pilger, M. Miceli and S. E. Levine
“The Double-Double Pluto-Charon and Pluto-Hydra Predicted Stellar Occultations of June 2011”
AAS Division of Planetary Sciences meeting
#EPSC-DPS2022-1821
Nantes October 2011
Zuluaga, C. A., M. J. Person, A. S. Bosh, S. E. Levine, A. A. S. Gulbis, A. M. Zangari, J. M. Pasachoff, B. A. Babcock, S. Pandey, D. Amrhein, S. Sallum, E. W. Dunham, D. J. Tholen, P. Collins, T. Bida, B. Taylor, R. Lucas, M. Kakkala, J. Ciotti, S. Plunkett, N. Hiraoka, W. Best, E. J. Pilger, M. Miceli, A. Springmann, M. Hicks, B. Thackeray, J. Emery, S. Rapoport, I. Ritchie, M. Pearson, A. Mattingly, J. Brimacombe, D. Gault, R. Jones, R. Nolthenius, J. Broughton, T. Barry
“The measured Pluto-Charon offset from the stellar occultations of 23 June 2011”
AAS Division of Planetary Sciences meeting
#EPSC-DPS2022-1866
Nantes
October 2011
Rusin, V., M. Saniga, J. M. Pasachoff, M. Druckmüller, and M. Belik
“Ten years of the high-resolution imaging process of the clipse white-light corona”
AGU Fall Meeting
Poster SH33A-2031
October 2011
POSTGRADUATE PLANS OF DEPARTMENT MAJORS
| Name | Plans |
|
Matthew W. Hosek |
Grad school in Astronomy, University of Hawaii at Manoa |
| Aven King | Scuba shop instructor |
| Ben Oliva | unknown |
| Taryn Siegel |
Epic (healthcare software in Wisconsin) |
Student Abstracts
ASTRONOMY
Integral-Field Spectroscopy of NGC 2392: The Eskimo Nebula
Matthew W. Hosek
I analyze observations of NGC 2392, a nearby planetary nebula known as the Eskimo Nebula. Planetary Nebulae are the remnants of low to intermediate mass stars (like our sun) that have run out of fuel and ejected their outer gas layers into the environment.
Monitoring Ha Emission-Line Stars in Open Clusters
Allen Davis, Williams College ’14, Yaron Teich, Vassar College, Advisor: Steven Souza, Williams College presented at the Keck Northeast Astronomy Consortium Student Research Symposium, September 2011, Wellesley College
We are continuing a multi-year project to monitor hydrogen (Hα) emission line variations in early-type stars, particularly Be stars. We use on-band (656 nm) and off-band (645 nm) filters to collect photometric data on hundreds of stars at a time, rather than looking spectroscopically at individual stars. We also refined our data reduction and processing methods. We have seen a significant rise in Hα emission by the known Be star VES 606 over several months.
FACULTY PUBLICATIONS
ASTRONOMY
Structure and Dynamics of the 11 July 2010 Eclipse White-Light Corona
Jay M. Pasachoff, Vojtech Rušin, Hana Druckmüllerová, Metod Saniga, Muzhou Lu, Craig Malamut, Daniel B. Seaton, Leon Golub, Alex J. Engell, Steele W. Hill, and Robert Lucas
Astrophysical Journal, 734, 114-123 (2012) http://stacks.iop.org/0004-637X/734/114
The white-light corona (WLC) during the total solar eclipse on 2010 July 11 was observed by several teams in the Moon’s shadow stretching across the Pacific Ocean and a number of isolated islands. We present a comparison of the WLC as observed by eclipse teams located on the Tatakoto Atoll in French Polynesia and on Easter Island, 83 minutes later, combined with near-simultaneous space observations. The eclipse was observed at the beginning of the solar cycle, not long after solar minimum. Nevertheless, the solar corona shows a plethora of different features (coronal holes, helmet streamers, polar rays, very faint loops and radial-oriented thin streamers, a coronal mass ejection, and a puzzling “curtain-like” object above the north pole). Comparing the observations from the two sites enables us to detect some dynamic phenomena. The eclipse observations are further compared with a hairy-ball model of the magnetic field and near-simultaneous images from the Atmospheric Imaging Assembly on NASA’s Solar Dynamics Observatory, the Extreme Ultraviolet Imager on NASA’s Solar Terrestrial Relations Observatory, the Sun Watcher, using Active Pixel System Detector and Image Processing on ESA’s PRoject for Onboard Autonomy, and the Naval Research Laboratory’s Large Angle and Spectrometric Coronagraph on ESA’s Solar and Heliospheric Observatory. The Ludendorff flattening coefficient is 0.156, matching the expected ellipticity of coronal isophotes at 2 R ☉, for this rising phase of the solar-activity cycle.
Sunlight Refraction in the Mesosphere of Venus During the Transit on June 8th, 2004
Tanga, P., T. Widemann, B. Sicardy, J. M. Pasachoff, J. Arnaud, L. Comolli, A. Rondi, S. Rondi, and P. Suetterlin
Icarus, 218, 207-219 (2012) http://dx.doi.org/10.1016/j.icarus.2011.12.004; http://arxiv.org/abs/1112.3136
http://www.sciencedirect.com/science/article/pii/S0019103511004696
Many observers in the past gave detailed descriptions of the telescopic aspect of Venus during its extremely rare transits across the Solar disk. In particular, at the ingress and egress, the portion of the planet’s disk outside the Solar photosphere has been repeatedly perceived as outlined by a thin, bright arc (“aureole”). Those historical visual observations allowed inferring the existence of Venus’ atmosphere, the bright arc being correctly ascribed to the refraction of light by the outer layers of a dense atmosphere. On June 8th, 2004, fast photometry based on electronic imaging devices allowed the first quantitative analysis of the phenomenon. Several observers used a variety of acquisition systems to image the event — ranging from amateur-sized to professional telescopes and cameras — thus collecting for the first time a large amount of quantitative information on this atmospheric phenomenon. In this paper, after reviewing some elements brought by the historical records, we give a detailed report of the ground based observations of the 2004 transit. Besides confirming the historical descriptions, we perform the first photometric analysis of the aureole using various acquisition systems. The spatially resolved data provide measurements of the aureole flux as a function of the planetocentric latitude along the limb. A new differential refraction model of solar disk through the upper atmosphere allows us to relate the variable photometry to the latitudinal dependency of scale-height with temperature in the South polar region, as well as the latitudinal variation of the cloud-top layer altitude. We compare our measurements to recent analysis of the Venus Express VIRTIS-M, VMC and SPICAV/SOIR thermal field and aerosol distribution. Our results can be used a starting point for new, more optimized experiments during the 2012 transit event.
Structure and Dynamics of the 2 July 2009 Eclipse White-Light Corona
Jay M.,Vojtech Rušin, Metod Saniga, Hana Druckmüllerová, and Bryce A. Babcock
Astrophysical Journal, 742, 29-42 (2011)
The white-light corona (WLC) during the total solar eclipse of 2009 July 22 was observed by several teams in the Moon’s shadow stretching from India and China across the Pacific Ocean with its many isolated islands. We present a comparison of the WLC as observed by eclipse teams located in China (Shanghai region) and on the Enewetak Atoll in the Marshall Islands, with observations taken 112 minutes apart, combined with near-simultaneous space observations. The eclipse was observed at the beginning of solar cycle 24, during a deep solar minimum (officially estimated as 2008 December according to the smoothed sunspot number, but very extended). The solar corona shows several different types of features (coronal holes, polar rays, helmet streamers, faint loops, voids, etc.), though it was extremely sparse in streamers as shown from Large-Angle Spectroscopic Coronagraph data. No large-scale dynamical phenomena were seen when comparing the observations from the two sites, confirming that the corona was quiescent. We measure a Ludendorff flattening coefficient of 0.238, typical of solar minimum.
Lomonosov, the Discovery of Venus’s Atmosphere, and Eighteenth-century Transits of Venus
Jay M. Pasachoff and William Sheehan
Journal for the History and Heritage of Astronomy, 15, (1), RPO, 1-12 (2012) http://adsabs.harvard.edu/abs
The discovery of Venus’s atmosphere has been widely attributed to the Russian academician M.V. Lomonosov from his observations of the 1761 transit of Venus from St. Petersburg. Other observers at the time also made observations that have been ascribed to the effects of the atmosphere of Venus. Though Venus does have an atmosphere one hundred times denser than the Earth’s and refracts sunlight so as to produce an ‘aureole’ around the planet’s disk when it is ingressing and egressing the solar limb, many eighteenth century observers also upheld the doctrine of cosmic pluralism: believing that the planets were inhabited, they had a preconceived bias for believing that the other planets must have atmospheres. A careful re-examination of several of the most important accounts of eighteenth century observers and comparisons with the observations of the nineteenth century and 2004 transits shows that Lomonosov inferred the existence of Venus’s atmosphere from observations related to the ‘black drop’, which has nothing to do with the atmosphere of Venus. Several observers of the eighteenth-century transits, includ-ing Chappe d’Auteroche, Bergman, and Wargentin in 1761 and Wales, Dymond, and Rittenhouse in 1769, may have made bona fide observations of the aureole produced by the atmosphere of Venus. Therefore, it appears that several observers-but not Lomonosov-should receive credit for first detecting the aureole due to refraction of sunlight by the atmosphere of Venus during a transit. This crucial observation occurred almost three decades before Johann Schroeter independently demonstrated the existence of the atmosphere of Venus from his analysis of extensions of the semicircle of light of the planet near inferior conjunction, which are produced by back-scattering of light by aerosol-sized particles.
Spectroscopic Coronal Observations during the Total Solar Eclipse of 11 July 2010
Voulgaris, Aris, Paul Gaintatzis, John H. Seiradakis, Jay M. Pasachoff, and Thanasis E. Economou
Solar Physics, 278, (1), 187-202; DOI:10.1007/s11207-012-9929-4 (2012)
The flash spectrum of the solar chromosphere and corona was measured with a slitless spectrograph before, after, and during the totality of the solar eclipse, of 11 July 2010, at Easter Island, Chile. This eclipse took place at the beginning of the 24th solar cycle, after an extended minimum of the solar-activity. The spectra taken during the eclipse show a different intensity ratio of the red and green coronal lines compared with those taken during the total solar eclipse of 1 August 2008, which took place towards the end of the 23rd solar cycle. The characteristic coronal forbidden emission line of [Fe XIV] (5303 Å) was observed in the east and west solar limbs in four areas relatively symmetrically located with respect to the solar rotation axis. Subtraction of the continuum flash-spectrum background led to the identification of several extremely weak emission lines, including [Ca XV] (5694 Å), which is normally detected only in regions of very high excitation, e.g., during flares or above large sunspots. The height of the chromosphere was measured spectrophotometrically, using spectral lines from light elements and compared with the equivalent height of the lower chromosphere measured using spectral lines from heavy elements
Abundances of Planetary Nebulae in the Outer Disk of M31
Karen B. Kwitter, Emma M. M. Lehman ’10, Bruce Balick, and Richard B. C. Henry
Astrophysical Journal, 753, 12 (2012)
We present spectroscopic observations and chemical abundances of 16 planetary nebulae (PNe) in the outer disk of M31. The [O III] λ4363 line is detected in all objects, allowing a direct measurement of the nebular temperature essential for accurate abundance determinations. Our results show that the abundances in these M31 PNe display the same correlations and general behaviors as Type II PNe in the Milky Way Galaxy. We also calculate photoionization models to derive estimates of central star properties. From these we infer that our sample PNe, all near the bright-end cutoff of the Planetary Nebula Luminosity Function, originated from stars near 2 solar masses. Finally, under the assumption that these PNe are located in M31’s disk, we plot the oxygen abundance gradient, which appears shallower than the gradient in the Milky Way.
Using Spectra to Determine Planetary Nebula Properties
Karen B. Kwitter and Richard B.C. Henry
The Classroom Astronomer, 9 (2011)
Planetary nebulae are hot glowing gas clouds ejected by dying low- to intermediate-mass stars. The nebulae glow because they are heated by energetic ultraviolet photons from the exposed stellar core. The light produced by a planetary nebula is an emission spectrum, with spikes of emission at specific wavelengths corresponding to the elements in the gas. A spectrum can be displayed as a picture showing colored stripes, or a graph. We have developed three exercises, all available online, for determining various properties related to planetary nebulae or their environs. These exercises make use of the “Gallery of Planetary Nebula Spectra” database at tinyurl.com/63ed7tx. The database contains optical spectra, shown as graphs, of more than 160 planetary nebulae that we and our colleagues have observed in the Milky Way Galaxy, along with distance and other information about them, links to images, references in the literature, and more.
Galactic Disk Abundance Gradients and the 10 kpc Rg Region
J.B. Milingo, R.B.C Henry, K.B. Kwitter and B. Balick
Bulletin of the American Astronomical Society, 441.05meeting in Austin, TX (January 2012)
We examine the radial abundance gradient in the Milky Way disk via homogeneously determined data for 124 Galactic planetary nebulae. With O, Ne, S, Cl, and Ar available and a range of galactocentric distance (Rg) from 0.9 to 21 kpc, we explore the gradient by statistically analyzing a series of short segments of increasing average Rg. Though the detailed nature of the radial gradient remains somewhat uncertain, we find the short segments support a discontinuity at Rg ~10 kpc, consistent with that shown via open clusters, hence providing a potential constraint on the dynamic history of the Galactic disk.
Reduce, Reuse, Recycle: Planetary Nebulae as Green Galactic Citizens
Karen B. Kwitter and Richard B. C. Henry
IAU Symposium #283, “Planetary Nebulae: An Eye to the Future”, Manchado, Stanghellini & Schönberner eds. (Cambridge) in press.
We review gas-phase abundances in PNe and describe their dual utility as archives of original progenitor metallicity via the alpha elements, as well as sources of processed material from nucleosynthesis during the star’s evolution, i.e., C, N, and s-process elements. We describe the analysis of PN spectra to derive abundances and discuss the discrepancies that arise from different choices at each step. Abundance results for the Milky Way and Magellanic Clouds from various groups of investigators are presented; the observational results are compared with theoretical predictions of AGB stellar yields. Finally, we suggest areas where more work is needed to improve our abilities to determine abundances in PNe.
Abundances of Disk Planetary Nebulae in M31 and the Radial Oxygen Gradient
Karen B. Kwitter, Emma M. M. Lehman ’10, Bruce Balick, and Richard B.C. Henry
IAU Symposium #283, “Planetary Nebulae: An Eye to the Future”, Manchado, Stanghellini & Schönberner eds. (Cambridge) in press.
We have obtained spectra of 16 planetary nebulae in the disk of M31 and determined the abundances of He, N, O, Ne, S and Ar. Here we present the median abundances and compare them with previous M31 PN disk measurements and with PNe in the Milky Way. We also derive the radial oxygen gradient in M31, which is shallower than that in the Milky Way, even accounting for M31′s larger disk scale length.
Further Exploration of Galactic Disk Abundance Gradients
J.B. Milingo, R.B.C. Henry, K. B. Kwitter, and B. Balick
IAU Symposium #283, “Planetary Nebulae: An Eye to the Future”, Manchado, Stanghellini & Schönberner eds. (Cambridge) in press.
With a compiled set of homogeneously determined abundances for 124 Galactic planetary nebulae (PNe), we examine the abundance gradient in the Milky Way disk. We present recent results from a detailed regression analysis of the oxygen gradient. With O, Ne, S, Cl, and Ar available for both Peimbert Types I and II PNe, and a range of galactocentric distance from 0.9 to 21 kpc, we present additional exploration of the disk abundance gradient by statistically analyzing a series of short segments of increasing average galactocentric distance. Finally, we further analyze the scatter observed in PNe abundances within these segments.
Luminosity and Abundance Correlations in a Carefully-Studied Sample of PNe
J. McKeever, B. Balick, K.B. Kwitter, K. Braxton, T. Gomes, J. Green, and R.B.C Henry
IAU Symposium #283, “Planetary Nebulae: An Eye to the Future”, Manchado, Stanghellini & Schönberner eds. (Cambridge) in press.
We report the results of empirical correlation studies of a homogeneously observed and analyzed set of 120 Galactic PNe spanning a wide range of distances, abundances, excitation, densities, and both major Peimbert types. Our goal is to continue the analysis of these data begun in Milingo et al 2010 and Henry et al 2010 who primarily examined correlations of abundances and with galactocentric radius Rgal. We find that a subsample of PNe chosen for their large [OIII] luminosities, L[OIII], generally show tighter abundance correlations as a function of log(O/H) than does the full sample. In addition to He/H and N/H, the abundances of Cl and Ar correlate with Peimbert types I and II. These results are not sensitive to the derived values of ionization correction factors, ICF. Finally, we show that L[OIII] rises and then falls when plotted against the physical radius Rneb of PNe, the latter a likely proxy for nebular age. This result nicely complements the studies of Frew 2008 (PhD thesis) who found a tight correlation of Hβ and [OIII] surface brightness with Rneb. [NII]/Hα and HeII 4686/Hβ ratios also correlate with Rneb, but the trends are scattered.
3D Ionization Structure & Kinematics of NGC 2392
R.J. Dufour, J.N. Sick, P.M. Hartigan, R.B.C. Henry, K.B. Kwitter, and J. Bohigas
IAU Symposium #283, “Planetary Nebulae: An Eye to the Future”, Manchado, Stanghellini & Schönberner eds. (Cambridge) in press.
We discuss the three dimensional morphology, ionization structure, and kinematics of NGC 2392, the “Eskimo,” based on new and archival HST imagery and new long-slit echelle and integral field spectroscopy. High spatial resolution 2D ionization maps of the nebula were made from the HST WFPC2 imagery and compared with maps of the emission-line structure in weaker diagnostic lines from the VIRUS-P IFS observations obtained at McDonald Observatory. Then high velocity resolution long-slit spectroscopy with the KPNO 4m echelle spectroscopy was used to map the kinematics and evaluate the 3D ionization structure of the nebula in several important ions, including C++ for the first time.
