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Macke R.J.,University of Central Florida | Consolmagno G.J.,Vatican Observatory | Britt D.T.,University of Central Florida | Hutson M.L.,Portland State University
Meteoritics and Planetary Science | Year: 2010

As part of our continuing survey of meteorite physical properties, we measured grain and bulk density, porosity, and magnetic susceptibility for 41 stones from 23 enstatite chondrites (ECs), all with masses greater than 10-g, representing the majority of falls and a significant percentage of all available non-Antarctic EC meteorites. Our sampling included a mix of falls and finds. For falls, grain densities range from 3.45 to 4.17-g-cm -3, averaging 3.66-g-cm -3; bulk densities range from 3.15 to 4.10-g-cm -3, averaging 3.55-g-cm -3; porosities range from 0 to 12% with the majority less than 7%, and magnetic susceptibilities (in log units of 10 -9-m 3-kg -1) from 5.30 to 5.64, with an average of 5.47. For finds, weathering reduces both grain and bulk densities as well as magnetic susceptibilities. On average, finds have much higher porosity than falls. The two EC subgroups EH and EL, nominally distinguished by total iron content, exhibit similar values for all of the properties measured, indicating similar metallic iron content in the bulk stones of both subgroups. We also observed considerable intra-meteorite variation, with inhomogeneities in bulk and grain densities at scales up to approximately 40-g (approximately 12-cm 3). © The Meteoritical Society, 2010. Source


Finkelman I.,Tel Aviv University | Brosch N.,Tel Aviv University | Jose G. Funes S.J.,Vatican Observatory | Kniazev A.Y.,South African Astronomical Observatory | Vaisanen P.,South African Astronomical Observatory
Monthly Notices of the Royal Astronomical Society | Year: 2010

We report the results of multicolour observations of 30 E/S0 galaxies with dust lanes. For each galaxy we obtained broad-band images and narrow-band images using interference filters isolating the Hα+[N II] emission lines to derive the amount and morphology of dust and ionized gas. To improve the wavelength coverage we retrieved data from the Sloan Digital Sky Survey and Two Micron All Sky Survey and combined these with our data. Ionized gas is detected in 25 galaxies and shows in most cases a smooth morphology, although knots and filamentary structure are also observed in some objects. The extended gas distribution closely follows the dust structure, with a clear correlation between the mass of both components. An extinction law by the extragalactic dust in the dark lanes is derived and is used to estimate the dust content of the galaxies. The derived extinction law is used to correct the measured colours for intrinsic dust extinction and the data are fitted with a stellar population synthesis model.We find that theHα emission and colours ofmost objects are consistent with the presence of an 'old' stellar population (~10 Gyr) and a small fraction of a young' population (~10-100 Myr). To check this we closely examine NGC5363, for which archival Spitzer/Infrared Array Camera and Galaxy Evolution Explorer data are available, as a representative dust-lane E/S0 galaxy of the sample. © 2010 The Authors. Journal compilation. © 2010 RAS. Source


Kiefer W.S.,Lunar and Planetary Institute | MacKe R.J.,University of Central Florida | MacKe R.J.,Boston College | Britt D.T.,University of Central Florida | And 2 more authors.
Geophysical Research Letters | Year: 2012

Accurate lunar rock densities are necessary for constructing gravity models of the Moon's crust and lithosphere. Most Apollo-era density measurements have errors of 2-5% or more and few include porosity measurements. We report new density and porosity measurements using the bead method and helium pycnometry for 6 Apollo samples and 7 lunar meteorites, with typical grain density uncertainties of 10-30kgm -3 (0.3-0.9%) and porosity uncertainties of 1-3%. Comparison between igneous grain densities and normative mineral densities show that these uncertainties are realistic and that the helium fully penetrates the pore space. Basalt grain densities are a strong function of composition, varying over at least 3270 kg m -3 (high aluminum basalt) to 3460 kg m -3 (high titanium basalt). Feldspathic highland crust has a bulk density of 2200-2600 kg m -3 and porosity of 10-20%. Impact basin ejecta has a bulk density of 2350-2600 kg m -3 and porosity of ∼20%. Copyright 2012 by the American Geophysical Union. Source


Gabor P.,Vatican Observatory
Proceedings of the International Astronomical Union | Year: 2010

Although a formation-flying space interferometer designed for exoplanet spectroscopy is feasible in principle, the novelty and cost of such an instrument is likely to remain daunting unless the scientific benefits of this technology are demonstrated by intermediary, precursor missions. Such instruments would represent intermediary steps in the real-life testing of the technology, and therefore, by the very reason of being intermediary, they may not have the resolving or collecting power needed for the study of the objects where biomarkers could be hoped to be detected, i.e., exo-Earths in the habitable zone of their stars. This paper examines the potential applications of such intermediary instruments. The direct line of thought focuses on exoplanetology (gas giants, protoplanetary discs, Neptunes, super-Earths, etc.); what we would like to stimulate is an exercise in lateral thinking, looking at what might an intermediary interferometric mission contribute to other fields of astrophysical research (galaxies, supernova precursors, planetary nebulae, molecular clouds, etc.). The paper raises the question of collaboration with astrophysicists studying areas other than exoplanets and its potential gains for the future of space interferometry. © 2011 International Astronomical Union. Source


Finkelman I.,Tel Aviv University | Funes S.J. J.G.,Vatican Observatory | Brosch N.,Tel Aviv University
Monthly Notices of the Royal Astronomical Society | Year: 2012

We report observations of 16 candidate polar-ring galaxies (PRGs) identified by the Galaxy Zoo project in the Sloan Digital Sky Survey (SDSS) data base. Deep images of five galaxies are available in the SDSS Stripe82 data base, while to reach similar depth we observed the remaining galaxies with the 1.8-m Vatican Advanced Technology Telescope. We derive integrated magnitudes and u-r colours for the host and ring components and show continuum-subtracted Hα+[Nii] images for seven objects. We present a basic morphological and environmental analysis of the galaxies and discuss their properties in comparison with other types of early-type galaxies. Follow-up photometric and spectroscopic observations will allow a kinematic confirmation of the nature of these systems and a more detailed analysis of their stellar populations. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS. Source

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