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  • 1
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    Outgassing behavior and composition of comet C/1999 S4 (LINEAR) during its disruption (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-05-19
    Description: The gas activity of comet C/1999 S4 (LINEAR) was monitored at radio wavelengths during its disruption. A runaway fragmentation of the nucleus may have begun around 18 July 2000 and proceeded until 23 July. The mass in small icy debris (〈/=30-centimeter radius) was comparable to the mass in the large fragments seen in optical images. The mass budget after breakup suggests a small nucleus ( approximately 100- to 300-meter radius) that had been losing debris for weeks. The HNC, H2CO, H2S, and CS abundances relative to H2O measured during breakup are consistent with those obtained in other comets. However, a deficiency in CH3OH and CO is observed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bockelee-Morvan, D -- Biver, N -- Moreno, R -- Colom, P -- Crovisier, J -- Gerard, E -- Henry, F -- Lis, D C -- Matthews, H -- Weaver, H A -- Womack, M -- Festou, M C -- New York, N.Y. -- Science. 2001 May 18;292(5520):1339-43.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Observatoire de Paris-Meudon, F-92195, Meudon, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11359003" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Detection of the water reservoir in a forming planetary system (2011)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2011-10-25
    Description: Icy bodies may have delivered the oceans to the early Earth, yet little is known about water in the ice-dominated regions of extrasolar planet-forming disks. The Heterodyne Instrument for the Far-Infrared on board the Herschel Space Observatory has detected emission lines from both spin isomers of cold water vapor from the disk around the young star TW Hydrae. This water vapor likely originates from ice-coated solids near the disk surface, hinting at a water ice reservoir equivalent to several thousand Earth oceans in mass. The water's ortho-to-para ratio falls well below that of solar system comets, suggesting that comets contain heterogeneous ice mixtures collected across the entire solar nebula during the early stages of planetary birth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hogerheijde, Michiel R -- Bergin, Edwin A -- Brinch, Christian -- Cleeves, L Ilsedore -- Fogel, Jeffrey K J -- Blake, Geoffrey A -- Dominik, Carsten -- Lis, Dariusz C -- Melnick, Gary -- Neufeld, David -- Panic, Olja -- Pearson, John C -- Kristensen, Lars -- Yildiz, Umut A -- van Dishoeck, Ewine F -- New York, N.Y. -- Science. 2011 Oct 21;334(6054):338-40. doi: 10.1126/science.1208931.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Leiden Observatory, Leiden University, Post Office Box 9513, 2300 RA Leiden, Netherlands. michiel@strw.leidenuniv.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22021851" target="_blank"〉PubMed〈/a〉
    Keywords: Evolution, Planetary ; Extraterrestrial Environment ; *Ice ; *Planets ; *Stars, Celestial ; *Steam
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Ocean-like water in the Jupiter-family comet 103P/Hartley 2 (2011)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2011-10-07
    Description: For decades, the source of Earth's volatiles, especially water with a deuterium-to-hydrogen ratio (D/H) of (1.558 +/- 0.001) x 10(-4), has been a subject of debate. The similarity of Earth's bulk composition to that of meteorites known as enstatite chondrites suggests a dry proto-Earth with subsequent delivery of volatiles by local accretion or impacts of asteroids or comets. Previous measurements in six comets from the Oort cloud yielded a mean D/H ratio of (2.96 +/- 0.25) x 10(-4). The D/H value in carbonaceous chondrites, (1.4 +/- 0.1) x 10(-4), together with dynamical simulations, led to models in which asteroids were the main source of Earth's water, with 〈/=10 per cent being delivered by comets. Here we report that the D/H ratio in the Jupiter-family comet 103P/Hartley 2, which originated in the Kuiper belt, is (1.61 +/- 0.24) x 10(-4). This result substantially expands the reservoir of Earth ocean-like water to include some comets, and is consistent with the emerging picture of a complex dynamical evolution of the early Solar System.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hartogh, Paul -- Lis, Dariusz C -- Bockelee-Morvan, Dominique -- de Val-Borro, Miguel -- Biver, Nicolas -- Kuppers, Michael -- Emprechtinger, Martin -- Bergin, Edwin A -- Crovisier, Jacques -- Rengel, Miriam -- Moreno, Raphael -- Szutowicz, Slawomira -- Blake, Geoffrey A -- England -- Nature. 2011 Oct 5;478(7368):218-20. doi: 10.1038/nature10519.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max-Planck-Institut fur Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany. hartogh@mps.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21976024" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 4
    Electronic Resource
    Electronic Resource
    New Molecular Species in Comet C/1995 O1 (Hale-Bopp) Observed with the Caltech Ssubmillimeter Observatory (1997)
    Springer
    Earth, moon and planets 78 (1997), S. 13-20 
    Details
    ISSN: 1573-0794
    Keywords: Comets ; composition ; radio observations ; spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present millimeter-wave observations of HNCO, HC3N, SO, NH2CHO, H13CN, and H3O+ in comet C/1995 O1 (Hale-Bopp)obtained in February–April, 1997 with the Caltech Submillimeter Observatory (CSO). HNCO, first detected at the CSO in comet C/1996B2 (Hyakutake), is securely confirmed in comet Hale-Bopp via observations of three rotational transitions. The derived abundance with respect to H2O is (4-13) × 10-4. HC3N, SO, and NH2CHO are detected for the first time in a comet. The fractional abundance of HC3N based on observations of three rotational lines is (1.9 ± 0.2) × 10-4. Four transitions of SO are detected and the derived fractional abundance, (2-8) ×10-3, is higher than the upper limits derived from UV observations of previous comets. Observations of NH2CHO imply a fractional abundance of (1-8) × 10-4. H3O is detected for the first time from the ground. The H13CN (3-2)transition is also detected and the derived HCN/H13CN abundance ratio is 90 ± 15, consistent with the terrestrial12C/13C ratio. In addition, a number of other molecular species are detected, including HNC, OCS, HCO+, CO+, and CN(the last two are first detections in a comet at radio wavelengths).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006281802554
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  • 5
    Electronic Resource
    Electronic Resource
    Long-term Evolution of the Outgassing of Comet Hale-Bopp From Radio Observations (1997)
    Springer
    Earth, moon and planets 78 (1997), S. 5-11 
    Details
    ISSN: 1573-0794
    Keywords: Comets ; C/1995 O1 (Hale-Bopp) ; radio observations ; molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract C/1995 O1 (Hale-Bopp) has been observed on a regular basis since August 1995 at millimetre and submillimetre wavelengths using IRAM, JCMT, CSO and SEST radio telescopes. The production rates of eight molecular species (CO, HCN, CH3OH, H2CO,H2S, CS, CH3CN,HNC) have been monitored as a function of heliocentric distance(rh from 7 AU pre-perihelion to 4 AU post-perihelion. As comet Hale-Bopp approached and receded from the Sun, these species displayed different behaviours. Far from the Sun, the most volatile species were found in general relatively more abundant in the coma. In comparison to other species, HNC, H2CO and CS showed a much steeper increase of the production rate with decreasing rh. Less than 1.5 AU from the Sun, the relative abundances were fairly stable and approached those found in other comets near 1 AU. The kinetic temperature of the coma, estimated from the relative intensities of the CH3OH and CO lines, increased with decreasing rh, from about10 K at 7 AU to 110 K around perihelion. The expansion velocity of the gaseous species, derived from the line shapes, also increased with a law close torh 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006229818484
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  • 6
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    Ethyl alcohol and sugar in comet C/2014 Q2 (Lovejoy) (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2015-10-25
    Description: The presence of numerous complex organic molecules (COMs; defined as those containing six or more atoms) around protostars shows that star formation is accompanied by an increase of molecular complexity. These COMs may be part of the material from which planetesimals and, ultimately, planets formed. Comets represent some of the oldest and most primitive material in the solar system, including ices, and are thus our best window into the volatile composition of the solar protoplanetary disk. Molecules identified to be present in cometary ices include water, simple hydrocarbons, oxygen, sulfur, and nitrogen-bearing species, as well as a few COMs, such as ethylene glycol and glycine. We report the detection of 21 molecules in comet C/2014 Q2 (Lovejoy), including the first identification of ethyl alcohol (ethanol, C 2 H 5 OH) and the simplest monosaccharide sugar glycolaldehyde (CH 2 OHCHO) in a comet. The abundances of ethanol and glycolaldehyde, respectively 5 and 0.8% relative to methanol (0.12 and 0.02% relative to water), are somewhat higher than the values measured in solar-type protostars. Overall, the high abundance of COMs in cometary ices supports the formation through grain-surface reactions in the solar system protoplanetary disk.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Collisional excitation of doubly and triply deuterated ammonia ND2H and ND3 by H2 (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-06
    Description: The availability of collisional rate coefficients is a prerequisite for an accurate interpretation of astrophysical observations, since the observed media often harbour densities where molecules are populated under non-local thermodynamic equilibrium conditions. In the current study, we present calculations of rate coefficients suitable to describe the various spin isomers of multiply deuterated ammonia, namely the ND 2 H and ND 3 isotopologues. These calculations are based on the most accurate NH 3 –H 2 potential energy surface available, which has been modified to describe the geometrical changes induced by the nuclear substitutions. The dynamical calculations are performed within the close-coupling formalism and are carried out in order to provide rate coefficients up to a temperature of T = 50 K. For the various isotopologues/symmetries, we provide rate coefficients for the energy levels below ~100 cm –1 . Subsequently, these new rate coefficients are used in astrophysical models aimed at reproducing the NH 2 D, ND 2 H and ND 3 observations previously reported towards the pre-stellar cores B1b and 16293E. We thus update the estimates of the corresponding column densities and find a reasonable agreement with the previous models. In particular, the ortho-to-para ratios of NH 2 D and NHD 2 are found to be consistent with the statistical ratios.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    Collisional excitation of singly deuterated ammonia NH2D by H2 (2014)
    Oxford University Press
    Details
    Publication Date: 2014-09-17
    Description: The availability of collisional rate coefficients with H 2 is a pre-requisite for interpretation of observations of molecules whose energy levels are populated under non-local thermodynamical equilibrium conditions. In the current study, we present collisional rate coefficients for the NH 2 D/para-H 2 ( J 2 = 0, 2) collisional system, for energy levels up to J = 7 7 ( E u ~ 735 K) and for gas temperatures in the range T = 5–300 K. The cross-sections are obtained using the essentially exact close-coupling (CC) formalism at low energy and at the highest energies, we used the coupled-states (CS) approximation. For the energy levels up to J = 4 2 ( E u ~ 215 K), the cross-sections obtained through the CS formalism are scaled according to a few CC reference points. These reference points are subsequently used to estimate the accuracy of the rate coefficients for higher levels, which is mainly limited by the use of the CS formalism. Considering the current potential energy surface, the rate coefficients are thus expected to be accurate to within 5 per cent for the levels below J = 4 2 , while we estimate an accuracy of 30 per cent for higher levels.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data (2014)
    Oxford University Press
    Details
    Publication Date: 2014-10-12
    Description: Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H $_2^{18}$ O transitions were carried out towards the high-mass star-forming region G34.26+0.15 with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument onboard the Herschel Space Observatory , as well as with ground-based single-dish telescopes. 10 HDO lines and three H $_2^{18}$ O lines covering a broad range of upper energy levels (22–204 K) were detected. We used a non-local thermal equilibrium 1D analysis to determine the HDO/H 2 O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H 2 O ratio is found to be lower in the hot core (~3.5 10 –4 –7.5 10 –4 ) than in the colder envelope (~1.0 10 –3 –2.2 10 –3 ). This is the first time that a radial variation of the HDO/H 2 O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modelled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of ~10 5  yr after the infrared dark cloud stage.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    Multi-line detection of O2towardρOphiuchi A (2012)
    EDP Sciences
    Details
    Publication Date: 2012-05-01
    Print ISSN: 0004-6361
    Electronic ISSN: 1432-0746
    Topics: Physics
    Published by EDP Sciences
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