Theoretical Studies, Astrophysics, and Cosmology

STOEGER and ARAÚJO (Universidade Federal do Rio de Janeiro) with their collaborators are completing their work on specifying the procedure for solving the Einstein field equations in observational coordinates with cosmological data functions in the case of general perturbations (including non-spherically symmetric perturbations to Friedmann-Lemaître-Robertson-Walker [FLRW]). They also continue to work on generalizing such solution schemes to cases involving a mixture of dust and vacuum energy (non-zero cosmological constant). Once that is done, they intend to use these to constrain the deviations from FLRW with both astronomical and cosmic microwave background radiation data.

STOEGER AND RIBEIRO (Physics Institute, Universidade Federal do Rio de Janeiro) completed the first phase of their work relating the galaxy luminosity function to the relativistic energy density and to number counts for different redshifts, and using this to test the CNOC2 redshift survey luminosity functions for consistency with the assumed Einstein de Sitter cosmology. This is a preliminary step to using number-count and observer-area distance data to constrain the large-scale structure of the universe without assuming that it is FLRW, and including a significant cosmological-constant contribution to the mass-energy, which may be driving the acceleration of the expansion of the universe we now detect. As mentioned last year, one strong motivation for this is to determine on what length scales the universe can be adequately described by an almost- (or perturbed) FLRW cosmological model. It is fairly clear from cosmic microwave background considerations that this is true on the largest scales. But what is the smallest scale on which it is true? We still do not know. In pursuing an answer to this question through application of these procedures to solve the field equations with astronomical data, we shall also have to assume a reasonable model of galaxy number and luminosity evolution.

ELLIS AND DUNSBY (Department of Mathematics, University of Cape Town) together with MAARTENS (School of Mathematical Sciences, University of Portsmouth) and STOEGER are continuing their work on investigating the constraints on epochs in both closed and open FLRW cosmologies, as well as their relation to the earlier Planck era, during which quantum gravity dominates. ELLIS, STOEGER, McEWAN (Cape Town), and DUNSBY have already published two preliminary papers on this subject focusing on closed FLRW models. The work also involves investigating the effect on the epoch of an earlier mixed radiation-vacuum energy (cosmological constant) epoch just after the Planck era, and whether or not there are situations in which the Planck era can be avoided. In connection with this, Stoeger continues to do research on the Planck-era processes that would determine the size and homogeneity necessary for the inflation of a patch of the very early universe.

JUST (Department of Physics, University of Arizona) and STOEGER have been progressing with their research on a number of areas in quantum theory of measurement and quantum field theory.

LISZKA (Swedish Institute of Space Science, Sförs), PACHOLCZYK (Steward Observatory, University of Arizona), and STOEGER completed a study of the effect of ROSAT spacecraft wobble on the X-ray variability data from Seyfert galaxies (using NGC 5548 as an example). They demonstrated that the low-level deterministic and quasi-periodic signals from such a source can be separated successfully from the wobble harmonics. This confirms the detection of such intrinsic signals in earlier analyses. They are continuing to pursue a variety of other observational and theoretical topics related to active galactic nuclei (AGN) X-ray emission, which is almost certainly connected with the presence of supermassive black holes, or clusters of black holes, in these objects.

WHITMAN has written about 100 pages on his project of exposing the real irreducible representations of real forms of the simple complex Lie algebras. Since he wished to give a readable background in which to locate the material, he sought to review some old material in an interesting manner. Starting with a knowledge of linear algebra, the project leads the reader to an understanding of the fundamental decomposition theorem of Lie algebras. Every Lie algebra over a field of characteristic zero can be decomposed into a linear space direct sum of a semi-simple Lie subalgebra and a solvable Lie subalgebra. The lack of uniqueness of the decomposition constitutes one of the most important tools for understanding this material. A platform for presenting this exposition is the Clavius Group of Mathematicians (see Section III).

In collaboration with a group of physicists and mathematicians from Krakow Astronomical Observatory and Warsaw Technical University, HELLER is pursuing a program to elaborate generalized methods of geometry and their applications to general relativity and cosmology. Substantial progress has been made in investigating the structure of malicious singularities in cosmology, such as the Big Bang singularity, and an extensive review paper has been published.

Extragalactic Research

The modeling of galaxy evolution requires a better understanding of the relationships between the large-scale star formation rate (SFR) and the physical properties of the parent galaxies. Star-forming galaxies in the local universe provide important clues for understanding the evolutionary properties of galaxies and the physical processes that drive that evolution. To explore these relationships, KENNICUTT (Steward Observatory), FUNES, SAKAI (University of California, Los Angeles), and AKIYAMA (Steward Observatory) obtained H-alpha images to complete a volume-limited survey of integrated SFRs for a complete sample of nearby galaxies within the local 11 megaparsec volume. They observed about 300 galaxies in the northern hemisphere and about 70 galaxies in the southern hemisphere. The observations were carried out with the Vatican Advanced Technology Telescope (VATT), the Steward Observatory 90-inch Bok Telescope at Kitt Peak, and the Cerro Tololo Interamerican Observatory 0.9-m telescope at Cerro Tololo, Chile. This program has the following aims: (1) to construct the local SFR distribution function as a reference for cosmological look-back studies; (2) to develop new diagnostic measures of the rate and distribution of star formation in galaxy populations; (3) to quantify the role of starbursts in the evolution of low-mass galaxies; (4) to quantify the incompleteness biases in star-formation surveys; (5) to study the environmental dependence of the SFR distribution function; and (6) to provide a reference catalog and image database for use by workers in the field.

NGC 5128 (Centaurus A) is the nearest giant elliptical galaxy and the nearest AGN (active galactic nuclei), with a supermassive black hole and a powerful radio source. It is also and the nearest galaxy with shells and contains a central dust lane and a populous globular cluster system. MINNITI (Pontifical Catholic University of Chile), REJKUBA (European Southern Observatory), FUNES, and AKIYAMA (Steward Observatory) used the Very Large Telescope in Chile to obtain images of NGC 5128 to identify the optical counterparts to bright CHANDRA X-ray point sources. Based on size, optical magnitude, and color, they identified 23 new globular clusters, bringing the total globular cluster X-ray sources in this galaxy to 33, and establishing that 30% of the X-ray point sources in NGC 5128 are associated with globular clusters.

	This upper photo is an R-band image of NGC 5128 (Centaurus A).
	This H-alpha image (bottom) shows the complex distribution of ionized gas in the disk component of this giant elliptical galaxy. Vatican Observatory astronomer José Funes, S.J. obtained the images with the 0.9-m telescope at Cerro Tololo Inter-American Observatory in May 2001. They were reduced by Sanae Akiyama of Steward Observatory.

FUNES, REJKUBA, MINNITI, AKIYAMA, and KENNICUTT have also used the Very Large Telescope optical images of the innermost regions of NGC 5128 to obtain color-magnitude and color-color diagrams. These diagrams reveal a mixture of populations. They identify young stars and blue clusters, plus old globular clusters, embedded in the dusty regions of the disk of NGC 5128. In addition, H-alpha images taken with the 0.9-m telescope at Cerro Tololo Inter-American Observatory show the complex distribution of ionized gas in the disk component. The researchers have identified ring-like and arc-like structures, diffuse and discrete HII regions, etc. Based on this data set, they are studying the star formation history of the disk of this galaxy.

The Milky Way and M31 are examples of bright spiral galaxies surrounded by several satellites. The study of satellite galaxies can provide information on the merging and aggregation processes which, according to the hierarchical clustering models, form the larger spiral galaxies we observe. With the aim of testing hierarchical models of galaxy formation, GUTIERREZ (Instituto de Astrofísica de Canarias), FUNES, PRADA (Centro Astronómico Hispano-Alemán), and AZZARO (Isaac Newton Group of Telescopes) are conducting an ongoing observational program with the VATT on Mt. Graham. The program comprises broadband photometry in the optical and in the H-alpha narrowband for both the parent and the satellite galaxies, taken from the compilation by Zaritsky et al. (1997). The aim of this study is to determine star formation properties of the sample galaxies.

FUNES continued to collaborate with BERTOLA, CORSINI, and PIZZELLA (University of Padua). They are conducting an observing program using the Very Large Telescope in Chile and the 6.5-m MMT in Arizona. The project is aimed at obtaining spectroscopic data that will allow an accurate investigation of the dark matter distribution within the optical regions of low-surface-brightness galaxies. The published data indicate the presence of a constant-density core dark halo. However, for different reasons, the ionized gas kinematical measurements may be affected by systematic errors. The use of stellar dynamics will allow the researchers to overcome such difficulties and will further constrain the central density radial profile of dark matter halos. Photometric data will also be taken with the VATT. The photometric radial profile will allow constraints to be placed on the mass distribution using dynamical models.

O'DONOGHUE (VORG visiting scholar, St. Lawrence University, Canton, NY) began collaboration with FISHER (Hampden-Sydney College, Virginia) on VLA radio observations of Straight-Angle Tailed Radio Galaxies. This research is funded by a grant from the State of Louisiana and took place at the Louisiana State University at Monroe.

OMIZZOLO and CRISTIANI (European Southern Observatory, Munich) are determining the luminosity function for a sample of about 800 X-ray emitting, bright quasar candidates. CORBALLY and O'DONOGUE (VORG visiting scholar, St. Lawrence University, Canton, NY) collaborated with OMIZZOLO to obtain with the Steward Observatory 2.3-m telescope the last in a set of low resolution, red region spectra of that sample. Data reduction was completed at the Department of Astronomy of the University of Padua. Also related to this work, OMIZZOLO and RAFANELLI (Department of Astronomy, University of Padua) are studying the spectral data for NGC 526, an active galaxy, to determine the kinematics of this interesting object. The spectra were taken at the observatories of ESO and at the Telescopio Nazionale Galileo, Canary Islands.

The Galaxy and Galactic Objects

This HR-diagram for the NStars project, derived from spectral types and Hipparcos parallaxes, shows that the stars scattering below the main sequence are really at larger distances than those reported in the Hipparcos parallax survey. The spectral types confirm they lie beyond 40pc.

The Nearby Stars (NStars) project to obtain spectra, spectral types, and basic parameters of the 3600 stars within 40 parsec of the sun and earlier than M0 spectral type reported great progress: some 90% of the spectra are now observed; over a third are classified; SIMPLEX fitting is being applied to the spectra to obtain the parameters of T_eff, log g, [M/H], and microturbulence while chromospheric activity indices are calibrated and being calculated. The NStars project and its goals were described in the previous two Annual Reports. This year, the initial collaborators GRAY and McFADDEN (Appalachian State University, Boone, North Carolina), GARRISON (David Dunlap Observatory, University of Toronto), and CORBALLY were greatly helped by O'DONOGHUE (VORG visiting scholar and St. Lawrence University, Canton, NY). She assisted with observing at Steward Observatory, at Cerro Tololo Interamerican Observatory (CTIO), and at David Dunlap Observatory (DDO), with analyzing the spectra, and with steady classification work. MORTARA (Raytheon and University of Arizona) and KNOX (St. Lawrence University, Canton, NY) also became involved with the project. The former ported GRAY's XMK program for doing visual spectra classification to the Windows environment, "Winmk", and worked on getting the correct chromospheric activity calibrations for the Steward data. The latter helped with the observing at DDO and at CTIO.

The collaborative investigation of heavily reddened stars in clusters and of peculiar stars continues. STRAIZYS, KAZLAUSKAS, and CERNIS (Vilnius, Lithuania), with spectral classifications from CORBALLY and observing support from BOYLE, have compared photometric and spectral classifications of 18 stars in Perseus. Three are likely pre-main-sequence objects, and five are suspected binaries. The nature of the interstellar reddening law in the cluster IC 348 seems normal, though perhaps not so in the reflection nebula NGC 1333. For the crowded dust clouds along the Galactic equator near the Camelopardalis, Perseus, and Cassiopeia border, ZDANAVICIUS, STRAIZYS (Vilnius, Lithuania), and CORBALLY find that the extinction is close to the normal law for infrared and optical wavelengths. However, the ultraviolet shows a slightly larger extinction than average. In a new investigation, CORBALLY started using the Steward Observatory 2.3-m telescope to obtain spectra of photometrically interesting stars in an Aries molecular cloud.

RUEGER (Diocese of Brooklyn), with the help of CORBALLY, continued to process the UBVRI observations of two fields in the North Galactic Pole (NGP), obtained with the VATT. STAGG (Fairfield, Connecticut) produced preliminary photometric reductions, which now need more precision and more objects included before the G-dwarf stars can be identified.

BOYLE, with collaborators PHILIP (Union College, Schenectady, New York), SMRIGLIO (University of Rome), DASGUPTA (Cardiff, Wales), JANUSZ (Krakow, Poland), and STRAIZYS, KAZLAUSKAS, LAUGALYS (Vilnius, Lithuania), continues to use the filters of the Strömvil photometric system to make CCD exposures on various star fields. One can determine from the very precise colors of the stars, derived from the observations, the temperatures and surface gravities of the stars. Observations for this program are made at the VATT, the USNO-Flagstaff 1-m telescope, the 1.5-m telescope of the Astronomical Observatory of Bologna at Loiano, Italy, and the 1.5-m telescope of the University of Arizona on Mt. Lemmon.

IGEA is studying Monte Carlo methods for the transfer of radiation, in collaboration with HUGGINS (Physics Department, New York University). He also participates in a research program on the chemistry of protoplanetary disks together with GLASSGOLD (Astronomy Department, University of California Berkeley) and NAJITA (National Optical Astronomy Observatories).

Planetary Sciences

Meteorites

· Meteorite Parent Body Structure: Meteorite porosity and asteroid structure continued to be a major focus of the work of CONSOLMAGNO. Two major review papers were submitted on this ongoing work in 2002. A compilation of all published meteorite porosity data, collected and analyzed by BRITT (University of Tennessee) and CONSOLMAGNO was revised and accepted at the journal Meteoritics and Planetary Sciences. Meanwhile, a major review chapter by BRITT, YEOMANS (Jet Propulsion Laboratory), HOUSEN (Boeing Aerospace), and CONSOLMAGNO on asteroid density and structure was revised and accepted for the Asteroids III book to be published at the end of 2002 by the University of Arizona Press.

In addition to this work, CONSOLMAGNO made density measurements of several SNC-class meteorites¾believed to have originated from the surface of Mars¾in the Vatican collection, and STRAIT (Alma College, Michigan) computed the pore space visible in thin sections of these meteorites using scanning electron microscope (SEM) backscatter images. This work puts new constraints on the structure of Mars, as the density values they found are significantly higher than those previously used in geophysical models of Mars. If these new measurements accurately reflect the density of the Martian crust, the size and composition of the core and mantle of Mars are much more strongly constrained (in order to match the known values of the mass and moment of inertia of Mars) than previously believed. On the other hand, to relax this constraint would mean that the SNC meteorites, though from Mars, would not be typical of Mars crustal rocks in general. Either possibility represents a significant shift in our understanding of that planet.

The low porosities found for the SNC meteorites also indicate that the process of breaking these meteorites from Mars and landing them on Earth did not significantly add microcracks to their structure. This implies that the higher porosities seen in ordinary chondrites may well be characteristic of their in situ (asteroidal) state.

· Microcrack Porosity: The thin-section work on SNC meteorites described above is part of a larger ongoing project to determine the nature of meteorite porosity by close examination of SEM backscatter images. Over the past year, STRAIT and CONSOLMAGNO examined the repeatability of the technique by looking at several hundred images of a thin section from one meteorite, Knyahinya, taken from the Vatican collection. The measured microcrack porosity tended to be higher at the edges of the section, where large cracks were evident. Several interior areas also had significantly higher porosity. These areas tend to have major cracks through the fabric of the section, large holes, or gaps at the edges of large inclusions. Some areas with low porosity were where large metal inclusions filled most or all of the image area. Nonetheless, the final data set averaged over the areas measured compute an average porosity of 4.8% + 2%, with about 8% of the total porosity being filled with weathering material, while the hand specimen of Knyahinya measured for porosity at the Vatican Observatory had a porosity of 4.7% + 1.8%.

The range of porosities determined in this extensive study of the surface of one meteorite thin section show a similar range to that determined from a limited number of random images used to represent the sample. This confirms the assumption made in previous work that one can draw conclusions about the porosity of a sample based on a limited number of images.

· Origin of Meteorites: One goal of studying meteorite porosity and structure is to understand how gas and dust in the early solar system could have been compressed into hard, well-formed rocks. From work at the Vatican Observatory and elsewhere, it is now understood that ordinary chondrites are well-compacted stones with porosities generally less than 10%, and this porosity exists mostly as microcracks emplaced into the rock long after it was formed and solidified. What processes could have formed and solidified these rocks? Pressure, temperature, and water lithify terrestrial rocks. But although all meteorites have experienced some metamorphism, most have not seen sufficient pressure, temperature, or aqueous alteration to account for their lithification. How did nebular dust become well-lithified meteorites?

Pressures of 1 to 10 gigapascal (GPa), ten thousand to a hundred thousand times the pressure of air at the surface of the Earth, are needed to compress terrestrial sandstones. These pressures are higher than found inside any but the largest asteroids. However, asteroids that collide with a relative impact velocity of 1 km/s, equivalent to orbits with eccentricity of circa 0.05 in the asteroid region, create an energy density at the point of impact equivalent to a gigapascal.

However, a 1 km/s impact velocity is a most difficult velocity to attain. At present, relative impact speeds in the asteroid belt are much higher than 1 km/s, resulting in collisions that shatter rocks rather than compacting them. On the other hand, in the early solar nebula, when particle velocities were controlled by nebular gas drag, millimeter-size particles coupled to the gas could have impacted meter-size or larger bodies at roughly 0.05 km/s. Such an impact would perhaps be enough to compress under-dense dust balls, but it would hardly have been enough to turn them into solid rocks. The impacted bodies, however, might have been coherent enough to participate in further accretion.

CONSOLMAGNO, WEIDENSCHILLING (Planetary Science Institute, Tucson), and BRITT have suggested a scenario where just the right collision speeds could be obtained. When Jupiter formed in the early solar nebula (perhaps also inducing the shock waves that melted bits of dust to form the "chondrules" ubiquitous in ordinary chondrites), it could perturb a 100-km planetesimal into an orbit whose eccentricity fluctuated from 0 to 0.1; 10-km bodies should attain eccentricities of 0.05, while smaller ones would be damped to low eccentricity until the gas dissipated. Though collisions of such perturbed bodies at such speeds would disrupt similar-size bodies, collisions of smaller impactors into larger targets would allow the target to survive. A series of such impacts could produce lithified regions in a more porous, unconsolidated matrix. Subsequent collisional disruptions would dissipate this matrix, but allow the lithified regions to survive as meteorites to the present day.

· Meteorite Magnetic Susceptibility Studies: Magnetic susceptibility ¾ the degree to which a material responds to an external magnetic field–may provide a versatile, rapid, and nondestructive way to quantify the amount of magnetic minerals (such as iron-nickel metal, magnetic oxides, and sulfides) on a large volume of material. These phases are quite distinctive from class to class among meteorites, and so measuring the susceptibility provides a reliable and nondestructive way to classify a large number of samples in a short period of time.

ROCHETTE (European Center for Research and Teaching in Geoscience and the Environment, Aix en Provence, France), SAGNOTTI and CHEVRIER (National Institute of Geophysics and Technology, Rome), CONSOLMAGNO, DENISE (National Museum of Natural History, Paris), FOLCO (Antarctic Museum of Siena), OSETE (Universidad Complutense Madrid), and PESONEN (University of Helsinki, Finland) continued work begun in 2001 and have assembled a database of magnetic susceptibility measurements on 975 stony meteorites from various European collections: Helsinki, Madrid, Paris, Prague, Rome, Siena, Vatican, and other smaller collections. Measurements on bulk samples (up to 400 g) with a large coil Kappabridge instrument take about one second. The meteorites can be left within their protective plastic bags, without any contact or specific preparation, and are subjected to a magnetic field weaker than the Earth's ambient field. This simple procedure thus allows the team to scan a whole collection in a couple of days without danger of contaminating the samples.

The average magnetic susceptibility for a given class of meteorite appears to characterize H, L, and LL classes well with little overlap. EL and EH classes are very homogeneous and show exactly the same average metal amount. R chondrites are the weakest magnetically. C chondrites have a large dispersion for a given type, with 1.3 orders of magnitude progression in metal or magnetite amount from CM to CH. In achondrites, large spreads are often encountered within a class, with a maximum for aubrite (2 orders of magnitude from Khor Temiki to Mount Egerton), indicating heterogeneous parent bodies. The distinct increase of metal content in howardite with respect to eucrite and diogenite mimics the lunar samples (regolith breccia versus rocks) behavior.

Some "outlying" meteorites, i.e., those with magnetic susceptibility values more than two standard deviations from the mean of their class, may well represent samples that have been misclassified or misidentified. In fact, the magnetic susceptibility measurements revealed several suspicious meteorite pieces in the Vatican collection (the most extensively studied collection to date), and their proper classification was subsequently made by examination of polished thin sections. In particular, the Vatican sample thought to be the carbonaceous chondrite Murray was found to be a terrestrial rock and not a meteorite; the sample labeled Luponnas is an LL, not a H, chondrite. Most intriguingly, the meteorite labeled Daniel's Kuil (an enstatite chondrite) has since been identified in thin section by MIDDLEFELDT (Johnson Space Center, Houston) to be either a howardite or the silicate portion of a mesosiderite, in either case making it a much more rare and precious sample than previously thought.

Magnetic susceptibility analysis has several potential future uses. Magnetic susceptibility scans of very large collections (such as the Antarctic meteorites) could classify many samples quickly, and historical collections like the Vatican's could be scanned to detect nonrepresentative or misclassified specimens. A magnetic susceptibility probe could be included on future missions to land spacecraft on asteroids or other solar system objects. Such a probe, weighing less than 50 g, would be the only petrological tool with a penetration depth (about 3 cm) sufficient to look past superficial "space weathering" effects. On Earth, a magnetic susceptibility probe could also provide an efficient way to distinguish meteorites from terrestrial rocks for Nomad, the Antarctic meteorite-hunter robot currently undergoing field testing.

· Lunar meteorites: RUSSELL and JEFFRIES (Natural History Museum, London) along with CONSOLMAGNO have begun a detailed combined petrologic and rare earth element (REE) study of lunar meteorites. The goal is to better understand how impact processing has affected the compositions of lunar components, and to attempt to disentangle the composition of the melts from which the earliest lunar rocks initially formed. The first samples studied were from the Dar Al Gani 400 meteorite, a lunar highland melt breccia in the Vatican collection, and from Northwest Africa 482, an anorthosite from the Natural History Museum collection.

Thick sections of these meteorites were prepared, petrologically characterized using SEM, and major elements determined by electron probe. The thin sections were then subjected to REE analyses with a 50 mm spatial resolution using the 213 nm inductively coupled plasma mass spectrograph probe at the Natural History Museum. Calculations were then made to determine the REE composition of the associated equilibrium melt for each lithic clast.

All phases exhibited unfractionated REE patterns and a positive Eu anomaly, with a greater range of values than seen previously. Apparently the impact process severely affected the local distribution of REEs in lunar shock melt breccias. However, some signatures of the initial REE pattern remain preserved within the lithic clasts and can be used to place constraints on the conditions experienced during the anorthite-forming period on the Moon.

· New Meteorite Acquisitions: A series of donations and trades has brought a number of new meteorites into the Vatican collection. Most notable was the donation of the meteorite Dhofar 081, found in the Sahara desert in 1999; it is the third lunar sample in our collection (which includes another Sahara meteorite, Dar al Gani 400, and the Apollo 17 sample donated to the Vatican in 1972). Also included in these new acquisitions are Bilanga (a diogenite that fell in Burkina Faso, formerly Upper Volta, in 1999); Dhofar 018 (a howardite found in Oman in 2000); Gao-Guenie (an H5 that fell in Burkina Faso in 1960); Northwest Africa 091 (an L6 found in the Sahara in 2000); Selma (an H5 found in Alabama in 1906); and a 1.3-kg polished slice of the anomalous iron meteorite Tishomingo, found in Oklahoma in 1965. In addition, we were given thin sections of the meteorites Dar al Gani 190 (type CO 5); Dar al Gani 412 (a rare CK 5); Dar al Gani 430 (C3); Ghubara (L5); Gold Basin (L4); Holbrook (L6); Huckitta (pallasite); and Northwest Africa 010 (H4).

In 2002, pieces of the meteorites Allegan, Bjurbole, and Dar al Gani 476 were loaned from the Vatican collection to the Cranbrook Museum of Science (near Detroit, Michigan) for a three-year display. In addition, loans for scientific research were made of samples of Epinal to STRAZULLA (Catania, Italy) for destructive irradiation to simulate space weathering; samples of Finmarken, Holbrook, and Mocs to COSMOVICI (CNR, Rome) for astrobiology studies; and a piece of Vigarano to BRUCATO (INAF, Naples) for spectra measurements. Some meteorites of the Vatican collection were placed on exposition at the meeting, "Impacts: Asteroids, Meteorites and Comets Meet the Earth," held in both Turin and Milan, Italy.

Kuiper Belt Objects

Kuiper Belt Objects (KBOs) are the subject of a continuing long-term observational program at the Vatican Advanced Technology Telescope. KBOs are large proto-cometary bodies found beyond the orbit of Neptune. Their cousins, the Centaur objects, spend most of their time in the Kuiper Belt, but their paths have already been perturbed into orbits that will eventually bring them close to the Sun, like comets. First discovered only ten years ago, KBOs represent a new population of objects in our own solar system that in many ways resemble the disks of matter now being discovered around other stars.

The primary KBO observers are TEGLER (Northern Arizona University), ROMANISHIN (University of Oklahoma), in collaboration with CONSOLMAGNO, and RETTIG (University of Notre Dame). Though bad weather dogged much of their spring 2002 observing run, the October run yielded three excellent nights with photometric clarity and sub-arcsecond seeing. From these observations, good colors and light curves for four new KBOs were obtained.

These latest measurements will help to test the controversial claim that objects with perihelion distance less than 40 AU divide into two separate color populations (instead of a more continuous distribution of colors among the objects). To date, the ongoing survey of Centaur and KBO colors includes accurate B-V and V-R colors for about 50 objects. There is now evidence for a pattern in the colors observed; though KBOs in excited orbits can range in color from gray to red, all 20 of the observed KBOs on low eccentricity and low inclination orbits with perihelion distances greater than 40 AU exhibit extremely red surface colors.

It is thought that the surfaces of these objects are primarily icy and thus originally colorless, but that long-term exposure to cosmic rays and UV light converts carbon-bearing species into more complex organic molecules with a distinctly red color. Very red KBOs are presumably those with older surfaces, while more "gray" objects have had their surfaces recently gardened either by impacts or by the outgasing and refreezing of volatile materials jetting from the interior of these comet-like bodies. Thus, understanding the distribution of colors can provide direct evidence on the nature and frequency of the resurfacing episodes, and give clues to the evolutionary history of the outer solar system.

Moons of Jupiter

On November 12, ARLOT and THUILLOT (Institute for Celestial Mechanics, Paris), and KIKWAYA with assistance from COSTA began a series of observations of Jupiter satellite mutual events at the Vatican Observatory's 60-cm Double Astrograph reflector in Castel Gandolfo. By precisely timing the moment when one satellite eclipses another, the dynamics of their gravity fields can be determined, which in turn provides details on the interiors of the satellites and of Jupiter itself. These mutual events are observable over a period of nine months every six years, and to best provide the data needed they require a network of observers recording events at a variety of times and places. The current set of mutual event observations are being coordinated worldwide by ARLOT.

History and Philosophy of Science; Interdisciplinary Studies

STOEGER continues to pursue a variety of projects on the relationship among the natural sciences, philosophy, and theology, including developing a more adequate theology of creation, examining the philosophy of relations and causes in a scientific context, and preparing for two conferences next year: The Capstone Conference on Scientific Perspectives on Divine Action, sponsored by the Center for Theology and the Natural Sciences (CTNS) and the Vatican Observatory (VO), is scheduled to be held in Castel Gandolfo in early September 2003. The University of San Francisco-CTNS-VO Conference on "Reductionsim and Emergence," is scheduled for early October 2003 at the university.

CARUANA continues to pursue studies in logic and science, in particular, on the nature of contradiction in Wittgenstein.

CORBALLY has been reflecting on the ethical issues that have arisen over having telescopes in the sensitive ecological site of Mount Graham, Arizona. His analysis and proposals toward resolving the conflict were helped by participants in the European Conference on Science and Religion and by O'DONOGHUE (VORG visiting scholar and St. Lawrence University, Canton, NY).