排序方式： 共有11条查询结果，搜索用时 31 毫秒
1.
Peter Jenniskens Emmanuel Jehin Remi A. Cabanac Christophe O. Laux Iain D. Boyd 《Meteoritics & planetary science》2004,39(4):609-616
Abstract— A meteor spectrum was recorded serendipitously at the European Southern Obrervatory (ESO) Very Large Telescope (VLT) during a long exposure in long‐slit spectroscopic mode with FORS1. The ?8 magnitude fireball crossed the narrow 1Î × 7î slit during the observation of a high z supernova in normal service mode operation on May 12, 2002. The spectrum covered the range of 637–1050 nm, where the meteor's air plasma emissions from N2, N, and O dominate. Carbon atom emission was not detected in the relatively unexplored wavelength range above 900 nm, but the observed upper limit was only 3 sigma less than expected from the dissociation of atmospheric CO2. The meteor trail was resolved along the slit, and the emission had a Gaussian distribution with a dimension of FWHM = 7.0 (±0.4) * sin(α) * H (km)/90 m, where α is the unknown angle between the orientation of the meteor path and slit and H the assumed altitude of the meteor in km. To our knowledge, this is the first observation of a spatially resolved spectrum across a meteor trail. Unlike model predictions, the plasma excitation temperature varied only from about 4,300 to 4,365 K across the trail, based on the ratio of atomic and molecular nitrogen emissions. Unfortunately, we conclude that this was because the meteor at 100 km altitude was out of focus. 相似文献
2.
E. Jehin D. Bockelée-Morvan N. Dello Russo J. Manfroid D. Hutsemékers H. Kawakita H. Kobayashi R. Schulz A. Smette J. Stüwe M. Weiler C. Arpigny N. Biver A. Cochran J. Crovisier P. Magain H. Rauer H. Sana R. J. Vervack H. Weaver J.-M. Zucconi 《Earth, Moon, and Planets》2009,105(2-4):343-349
We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very Large Telescope. Such multi-wavelength and coordinated observations are a good example of what can be done to support space missions. From high resolution optical spectroscopy of the CN (0,0) 388 nm and NH2 (0,9,0) 610 nm bands using UVES at UT2 we determined 12C/13C = 90 ± 10 and 14N/15N = 150 ± 20 in CN and we derived a nuclear spin temperature of NH3 of 29 ± 1 K. These values are similar to those found in Oort-Cloud and Jupiter Family comets. From low resolution long slit spectroscopy with FORS1 at UT2 we determined the CN, C3 and C2 production rates and the parent and daughter scale lengths up to 5.2 105 km tailward. From high resolution IR spectroscopy with CRIRES at UT1 we measured simultaneously the production rates and mixing ratios of H2O, HCN, C2H2, CH4, C2H6, and CH3OH. 相似文献
3.
P. Hartogh E. Lellouch M. Banaszkiewicz E.A. Bergin N. Biver M.I. Blecka D. Bockelée-Morvan J. Cernicharo G. Davis P. Encrenaz A. González T. de Graauw D. Hutsemékers E. Jehin M. Kidger A. de Lange D.C. Lis J. Manfroid R. Moreno G. Orton M. Rengel M. Sánchez-Portal S. Sidher B. Swinyard N. Thomas B. Vandenbussche C. Waelkens 《Planetary and Space Science》2009,57(13):1596-1606
“Water and related chemistry in the Solar System” is a Herschel Space Observatory Guaranteed-Time Key Programme. This project, approved by the European Space Agency, aims at determining the distribution, the evolution and the origin of water in Mars, the outer planets, Titan, Enceladus and the comets. It addresses the broad topic of water and its isotopologues in planetary and cometary atmospheres. The nature of cometary activity and the thermodynamics of cometary comae will be investigated by studying water excitation in a sample of comets. The D/H ratio, the key parameter for constraining the origin and evolution of Solar System species, will be measured for the first time in a Jupiter-family comet. A comparison with existing and new measurements of D/H in Oort-cloud comets will constrain the composition of pre-solar cometary grains and possibly the dynamics of the protosolar nebula. New measurements of D/H in giant planets, similarly constraining the composition of proto-planetary ices, will be obtained. The D/H and other isotopic ratios, diagnostic of Mars’ atmosphere evolution, will be accurately measured in H2O and CO. The role of water vapor in Mars’ atmospheric chemistry will be studied by monitoring vertical profiles of H2O and HDO and by searching for several other species (and CO and H2O isotopes). A detailed study of the source of water in the upper atmosphere of the Giant Planets and Titan will be performed. By monitoring the water abundance, vertical profile, and input fluxes in the various objects, and when possible with the help of mapping observations, we will discriminate between the possible sources of water in the outer planets (interplanetary dust particles, cometary impacts, and local sources). In addition to these inter-connected objectives, serendipitous searches will enhance our knowledge of the composition of planetary and cometary atmospheres. 相似文献
4.
The Deep Impact mission succeeded in excavating inner materials from the nucleus of Comet 9P/Tempel 1 on 2005 July 04 (at 05:52 UT). Comet 9P/Tempel 1 is one of Jupiter family short period comets, which might originate in the Kuiper belt region in the solar nebula. In order to characterize the comet and to support the mission from the ground-based observatory, optical high-dispersion spectroscopic observations were carried out with the echelle spectrograph (UVES) mounted on the 8-m telescope VLT (UT2) before and after the Deep Impact event. Ortho-to-para abundance ratios (OPRs) of cometary ammonia were determined from the NH2 emission spectra. The OPRs of ammonia on July 3.996 UT and 4.997 UT were derived to be 1.28±0.07 (nuclear spin temperature: Tspin=24±2 K) and 1.26±0.08 (Tspin=25±2 K), respectively. There is no significant change between before and after the impact. Actually, most materials ejected from the impact site could have moved away from the nucleus on July 4.997 UT, about 17 h after the impact. However, a small fraction of the ejected materials might remain in the slit of UVES instrument at that time because an excess of about 20% in the NH2 emission flux is observed above the normal activity level was found [Manfroid, J., Hutsemékers, D., Jehin, E., Cochran, A.L., Arpigny, C., Jackson, W.M., Meech, K.J., Schulz, R., Zucconi, J.-M., 2007. Icarus. This issue]. If the excess of NH2 on July 04.997 UT was produced from icy materials excavated by the Deep Impact, then an upper-limit of the ammonia OPR would be 1.75 (Tspin>17 K) for those materials. On the other hand, the OPR of ammonia produced from the quiescent sources was similar to that of the Oort cloud comets observed so far. This fact may imply that physical conditions where cometary ices formed were similar between Comet 9P/Tempel 1 and the Oort cloud comets. 相似文献
5.
6.
Jehin Emmanuel Boehnhardt Hermann Sekanina Zdenek Bonfils Xavier Schütz Oliver Beuzit Jean-Luc Billeres Malvina Garradd Gordon J. Leisy Pierre Marchis Franck Más Antonio Origlia Livia Scarpa Daniel Thomas Daniel Tozzi Gian Paolo 《Earth, Moon, and Planets》2002,90(1-4):147-151
Comet C/2001 A2 experienced several splitting events duringits 2001 perihelion passage. The first break-upevent was observed
in March 2001 (IAUC 7616).In this paper we report the first results of ourextensive imaging and spectroscopic monitoring campaignwith
ESO telescopes over several weeks before andafter the perihelion passage on May 25 2001. 相似文献
7.
Benoît Carry Pierre Vernazza Christophe Dumas William J. Merline Olivier Mousis Philippe Rousselot Emmanuël Jehin Jean Manfroid Marcello Fulchignoni Jean-Marc Zucconi 《Icarus》2012,217(1):20-26
Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that will be studied by the NASA Dawn spacecraft via imaging, visible and near-infrared spectroscopy, and gamma-ray and neutron spectroscopy. While Ceres’ visible and near-infrared disk-integrated spectra have been well characterized, little has been done about quantifying spectral variations over the surface. Any spectral variation would give us insights on the geographical variation of the composition and/or the surface age. The only work so far was that of Rivkin and Volquardsen ([2010], Icarus 206, 327) who reported rotationally-resolved spectroscopic (disk-integrated) observations in the 2.2–4.0 μm range; their observations showed evidence for a relatively uniform surface.Here, we report disk-resolved observations of Ceres with SINFONI (ESO VLT) in the 1.17–1.32 μm and 1.45–2.35 μm wavelength ranges. The observations were made under excellent seeing conditions (0.6″), allowing us to reach a spatial resolution of ～75 km on Ceres’ surface. We do not find any spectral variation above a 3% level, suggesting a homogeneous surface at our spatial resolution. Slight variations (about 2%) of the spectral slope are detected, geographically correlated with the albedo markings reported from the analysis of the HST and Keck disk-resolved images of Ceres (Li et al. [2006], Icarus 182, 143; Carry et al. [2008], Astron. Astrophys. 478, 235). Given the lack of constraints on the surface composition of Ceres, however, we cannot assert the causes of these variations. 相似文献
8.
New independent constraints on the amount of water delivered to Earth by comets are derived using the 15N/14N isotopic ratio, measured to be roughly twice as high in cometary CN and HCN as in the present Earth. Under reasonable assumptions, we find that no more than a few percent of Earth’s water can be attributed to comets, in agreement with the constraints derived from D/H. Our results also suggest that a significant part of Earth’s atmospheric nitrogen might come from comets. Since the 15N/14N isotopic ratio is not different in Oort-cloud and Kuiper-belt comets, our estimates apply to the contribution of both types of objects. 相似文献
9.
Colin Snodgrass Jessica Agarwal Michael Combi Alan Fitzsimmons Aurelie Guilbert-Lepoutre Henry H. Hsieh Man-To Hui Emmanuel Jehin Michael S. P. Kelley Matthew M. Knight Cyrielle Opitom Roberto Orosei Miguel de Val-Borro Bin Yang 《Astronomy and Astrophysics Review》2017,25(1):5
We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies. 相似文献
10.
E. Jehin J. Manfroid D. Hutsemékers C. Arpigny J.-M. Zucconi 《Earth, Moon, and Planets》2009,105(2-4):167-180
Isotopic abundance ratios are excellently suited to probe the origin of solar system matter. We review the recent measurements of the isotopic ratios of the light elements (D/H, 12C/13C, 16O/18O, 14N/15N, 32S/34S) in cometary dust and gas and discuss briefly their implications. Special emphasis will be put on the determinations and progress performed in the field over the past years thanks to high resolution spectroscopy of cometary comae obtained with the ESO Very Large Telescope. Future perspectives from space missions and ground-based observations with new large and extremely large telescopes operating in the optical, infrared and submillimeter wavelengths will be presented. 相似文献