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1.
The chemical composition of comet nuclei derived from current data on interstellar dust ingredients and comet dust and coma
molecules are shown to be substantially consistent with each other in both refractory and volatile components. When limited
by relative cosmic abundances the water in comet nuclei is constrained to be close to 30% by mass and the refractory to volatile
ratio is close to 1:1. The morphological structure of comet nuclei, as deduced from comet dust infrared continuum and spectral
emission properties, is described by a fluffy (porous) aggregate of tenth micron silicate core-organic refractory mantle particle
on which outer mantles of predominantly H2O ices contain embedded carbonaceous and polycyclic aromatic hydrocarbon (PAH) type particles of size in the of 1 - 10nm range.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Alain Abergel Laurent Verstraete Christine Joblin René Laureijs Marc-Antoine Miville-Deschênes 《Space Science Reviews》2005,119(1-4):247-271
Infrared spectroscopy and photometry with ISO covering most of the emission range of the interstellar medium has led to important
progress in the understanding of the physics and chemistry of the gas, the nature and evolution of the dust grains and also
the coupling between the gas and the grains. We review here the ISO results on the cool and low-excitation regions of the
interstellar medium, where T
gas≲ 500 K, n
H∼ 100–105 cm−3 and the electron density is a few 10−4.
JEL codes: D24, L60, 047
Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries:
France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA. 相似文献
3.
The determination of the chemical composition of solid cometary dust particles was one of the prime objectives of the three
missions to Comet Halley in 1986. The dust analysis was performed by time-of-flight mass-spectrometry. Within the experimental
uncertainty the mean abundances of the rock-forming elements in cometary dust particles are comparable to their abundances
in CI-chondrites and in the solar photosphere, i.e. they are cosmic. H, C, and N, on the other hand, in cometary dust are
significantly more abundant than in CI-chondrites, approach solar abundances, are to some extent related to O, and reside
in an omnipresent refractory organic component dubbed CHON. Element variations between individual dust grains are characterized
by correlations of Mg, Si, and O, and to a lesser extent of Fe and S. From particle-to-particle variations of the rock forming
elements information on the mineralogy of cometary dust can be obtained. Cluster analysis revealed certain groups that partly
match the classifications of stratospheric interplanetary dust particles. About half of Halley's analyzed particles are characterized
by anhydrous Fe-poor Mg-silicates, Fe-sulfides, and rarely Fe metal. The Fe-poor Mg-silicates link Halley's dust to that of
Hale-Bopp as shown by recent IR observations. No significant deviation from normal of the isotopic composition of the elements is unequivocally present with the notable exception carbon: 12C-rich grains with 12C/13C-ratios up to ≈ 5,000 link cometary dust to presolar circumstellar grains identified in certain chondrites.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
Rosine Lallement 《Space Science Reviews》2007,130(1-4):341-353
The local Interstellar Medium (ISM) at the 500 pc scale is by many respects a typical place in our Galaxy made of hot and tenuous gas cavities blown by stellar winds and supernovae, that includes the 100 pc wide “Local Hot Bubble (LHB)”, dense and cold clouds forming the cavity “walls”, and finally diffuse and warm clouds embedded within the hot gas, such as the Local Interstellar Cloud (LIC) presently surrounding the Sun. A number of measurements however, including abundance data, have contradicted this “normality” of our interstellar environment. Some contradictions have been explained, some not. I review recent observations at different spatial scales and discuss those peculiarities. At all scales Johannes Geiss has played a major role. At the scale of the first hundred parsecs, there are at least three “anomalies”: (i) the peculiar Gould Belt (GB), (ii) the recently measured peculiar Deuterium abundance pattern, (iii) the low value of the local O, N and 3He gas phase abundances. I discuss here the possibility of a historical link between these three observations: the large scale phenomenon which has generated the Belt, a giant cloud impact or an explosive event could be the common origin. At the 50–100 parsec scale, some of the unexplained or contradictory measurements of the Local Bubble hot gas, including its EUV/soft X ray emissions, ion column-densities and gas pressure may at least partially be elucidated in the light of the newly discovered X-ray emission mechanism following charge transfer between solar wind high ions and solar system neutrals. The Local Bubble hot gas pressure and temperature may be lower than previously inferred. Finally, at the smaller scale of the local diffuse cloudlets (a few parsecs), the knowledge of their structures and physical states has constantly progressed by means of nearby star absorption spectroscopy. On the other hand, thanks to anomalous cosmic rays and pickup ions measurements, local abundances of ISM neutral species are now precisely derived and may be compared with the absorption data. Interestingly these comparisons are now accurate enough to reveal other (noninterstellar) sources of pickup ions. However the actual physical state of the ISM 10–20,000 A.U. ahead along the Sun trajectory, which will be the ambient interstellar medium in a few thousands years, remains unknown. Local Bubble hot gas or warm LIC-type gas? More EUV/UV spectroscopic data are needed to answer this question. 相似文献
5.
J. L. Linsky 《Space Science Reviews》2007,130(1-4):367-375
Analysis of UV spectra obtained with the HST, FUSE and other satellites provides a new understanding of the deuterium abundance
in the local region of the galactic disk. The wide range of gas-phase D/H measurements obtained outside of the Local Bubble
can now be explained as due to different amounts of deuterium depletion on carbonaceous grains. The total D/H ratio including
deuterium in the gas and dust phases is at least 23 parts per million of hydrogen, which is providing a challenge to models
of galactic chemical evolution. Analysis of HST and ground-based spectra of many lines of sight to stars within the Local
Bubble have identified interstellar velocity components that are consistent with more than 15 velocity vectors. We have identified
the structures of 15 nearby warm interstellar clouds on the basis of these velocity vectors and common temperatures and depletions.
We estimate the distances and masses of these clouds and compare their locations with cold interstellar clouds. 相似文献
6.
P. C. Frisch 《Space Science Reviews》2007,130(1-4):355-365
The properties of interstellar matter at the Sun are regulated by our location with respect to a void in the local matter
distribution, known as the Local Bubble. The Local Bubble (LB) is bounded by associations of massive stars and fossil supernovae
that have disrupted dense interstellar matter (ISM), driving low density intermediate velocity ISM into the void. The Sun
appears to be located in one of these flows of low density material. This nearby interstellar matter, dubbed the Local Fluff,
has a bulk velocity of ∼19 km s−1 in the local standard of rest. The flow is coming from the direction of the gas and dust ring formed where the Loop I supernova
remnant merges into the LB. Optical polarization data suggest that the local interstellar magnetic field lines are draped
over the heliosphere. A longstanding discrepancy between the high thermal pressure of plasma filling the LB and low thermal
pressures in the embedded Local Fluff cloudlets is partially mitigated when the ram pressure component parallel to the cloudlet
flow direction is included. 相似文献
7.
Methods and results of investigations of the interstellar gas inside the heliosphere are summarized and discussed. Flow parameters of H and He and the relative abundances of H, He, N, O, and Ne in the distant heliosphere are given. Charge exchange processes in front of the heliosphere affect the flow of hydrogen and oxygen through the heliopause. The speed of hydrogen is reduced by 6 km/s, and screening leads to a reduction of the O/He and H/He ratios in the neutral gas entering the heliosphere. When the screening effect and the acceleration processes leading to the anomalous cosmic rays (ACR) are sufficiently understood, abundances in the LIC can be derived from measurements inside the heliosphere. Since isotopic ratios are virtually not changed by screening or by EUV and solar wind ionisation, relative abundances of isotopes in the gaseous phase of the LIC can be determined with no or minor correction from investigations of the neutral gas, pickup ions and ACR particles. 相似文献
8.
Harald Krüger Markus Landgraf Nicolas Altobelli Eberhard Grün 《Space Science Reviews》2007,130(1-4):401-408
The Ulysses spacecraft has been orbiting the Sun on a highly inclined ellipse almost perpendicular to the ecliptic plane (inclination
79°, perihelion distance 1.3 AU, aphelion distance 5.4 AU) since it encountered Jupiter in 1992. The in situ dust detector
on board continuously measured interstellar dust grains with masses up to 10−13 kg, penetrating deep into the solar system. The flow direction is close to the mean apex of the Sun’s motion through the
solar system and the grains act as tracers of the physical conditions in the local interstellar cloud (LIC). While Ulysses
monitored the interstellar dust stream at high ecliptic latitudes between 3 and 5 AU, interstellar impactors were also measured
with the in situ dust detectors on board Cassini, Galileo and Helios, covering a heliocentric distance range between 0.3 and
3 AU in the ecliptic plane. The interstellar dust stream in the inner solar system is altered by the solar radiation pressure
force, gravitational focussing and interaction of charged grains with the time varying interplanetary magnetic field. We review
the results from in situ interstellar dust measurements in the solar system and present Ulysses’ latest interstellar dust
data. These data indicate a 30° shift in the impact direction of interstellar grains w.r.t. the interstellar helium flow direction,
the reason of which is presently unknown. 相似文献
9.
The present state of knowledge as regards interstellar dust is reviewed in Section 1 (Introduction); Section 2 (Composition of Dust Grains: graphite, silicate, dirty-ice, diamond); Section 3 (Size of Grains: mainly r 10–6 cm); Section 4 (Charge and Temperature of Grains: charge varies from 1–10 electrons (H i clouds) to 500 electrons (H ii clouds); temperature of grain material is about 10–20 K); Section 5 (Distribution and Origin of Grains: confined mainly to discs and arms of spiral galaxies, having had a passive origin by efflux from late-type stars or carbon-stars); Section 6 (Cosmogonical and Cosmological Aspects of Interstellar Grains: accretion by electrical-image forces of one dust grain onto a similarly-charged grain links up the absence of dust and gas in elliptical galaxies with the absence of a magnetic field of the type found in spirals. The origin of the 3 K background radiation field could be produced by a population of rotating silicate grains of r 10–7 cm); Section 7 (Conclusion). 相似文献
10.
A. J. Westphal A. M. Davis J. Levine M. J. Pellin M. R. Savina 《Space Science Reviews》2007,130(1-4):451-456
Galactic cosmic rays probably predominantly originate from shock-accelerated gas and dust in superbubbles. It is usually assumed
that the shock-accelerated dust is quickly destroyed by sputtering. However, it may be that some of the dust can survive bombardment
by the high-metallicity gas in the superbubble interior, and that some of that dust has been incorporated into solar system
materials. Interplanetary dust particles (IDPs) contain enigmatic submicron components called GEMS (Glass with Embedded Metal
and Sulfides). These GEMS have properties that closely match those expected of a population of surviving shock-accelerated
dust at the GCR source (Westphal and Bradley in Astrophys. J. 617:1131, 2004). In order to test the hypothesis that GEMS are synthesized from shock-accelerated dust in superbubbles, we plan to measure
the relative abundances of Fe, Zr, and Mo isotopes in GEMS using the new Resonance Ionization Mass Spectrometer at Argonne
National Laboratory. If GEMS are synthesized from shock-accelerated dust in superbubbles, they should exhibit isotopic anomalies
in Fe, Zr and Mo: specificially, enhancements in the r-only isotopes 96Zr and 100Mo, and separately in 58Fe, should be observed. We review also recent developments in observations of GEMS, laboratory synthesis of GEMS-like materials,
and implications of observations of GEMS-like materials in Stardust samples. 相似文献
11.
Ulysses measurements yield reliable in-situdetection of large dust particles which stem from the interstellar medium (ISM) and which
are not observed in interstellar extinction data. Both current models of large grains in the ISM: core-mantle grains as well
as composite grains, are in agreement with dust properties implied by the Ulysses results. However, the size of particles detected by Ulysses still exceeds the size of the large grains that are predicted for the ISM.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
Waves and instabilities in dusty space plasmas 总被引:1,自引:0,他引:1
Frank Verheest 《Space Science Reviews》1996,77(3-4):267-302
13.
Peter Hoppe 《Space Science Reviews》2008,138(1-4):43-57
Primitive meteorites and interplanetary dust particles contain small quantities of dust grains with highly anomalous isotopic compositions. These grains formed in the winds of evolved stars and in the ejecta of stellar explosions, i.e., they represent a sample of circumstellar grains that can be analyzed with high precision in the laboratory. Such studies have provided a wealth of information on stellar evolution and nucleosynthesis, Galactic chemical evolution, grain growth in stellar environments, interstellar chemistry, and the inventory of stars that contributed dust to the Solar System. Among the identified circumstellar grains in primitive solar system matter are diamond, graphite, silicon carbide, silicon nitride, oxides, and silicates. Circumstellar grains have also been found in cometary matter. To date the available information on circumstellar grains in comets is limited, but extended studies of matter returned by the Stardust mission may help to overcome the existing gaps. 相似文献
14.
Jack J. Lissauer 《Space Science Reviews》2005,116(1-2):11-24
Models of the origins of gas giant planets and ‘ice’ giant planets are discussed and related to formation theories of both
smaller objects (terrestrial planets) and larger bodies (stars). The most detailed models of planetary formation are based
upon observations of our own Solar System, of young stars and their environments, and of extrasolar planets. Stars form from
the collapse, and sometimes fragmentation, of molecular cloud cores. Terrestrial planets are formed within disks around young
stars via the accumulation of small dust grains into larger and larger bodies until the planetary orbits become well enough
separated that the configuration is stable for the lifetime of the system. Uranus and Neptune almost certainly formed via
a bottom-up (terrestrial planet-like) mechanism; such a mechanism is also the most likely origin scenario for Saturn and Jupiter. 相似文献
15.
The formation of planetary systems is intimately tied to the question of the evolution of the gas and solid material in the
early nebula. Current models of evolution of circumstellar disks are reviewed here with emphasis on the so-called “alpha models”
in which angular momentum is transported outward by turbulent viscosity, parameterized by an dimensionless parameter α. A
simple 1D model of protoplanetary disks that includes gas and embedded particles is used to introduce key questions on planetesimal
formation. This model includes the aerodynamic properties of solid ice and rock grains to calculate their migration and growth.
We show that the evolution of the nebula and migration and growth of its solids proceed on timescales that are generally not
much longer than the timescale necessary to fully form the star-disk system from the molecular cloud. Contrary to a widely
used approach, planet formation therefore can neither be studied in a static nebula nor in a nebula evolving from an arbitrary initial condition. We propose a simple approach to both account for sedimentation
from the molecular cloud onto the disk, disk evolution and migration of solids.
Giant planets have key roles in the history of the forming Solar System: they formed relatively early, when a significant
amount of hydrogen and helium were still present in the nebula, and have a mass that is a sizable fraction of the disk mass
at any given time. Their composition is also of interest because when compared to the solar composition, their enrichment
in elements other than hydrogen and helium is a witness of sorting processes that occured in the protosolar nebula. We review
likely scenarios capable of explaining both the presence of central dense cores in Jupiter, Saturn, Uranus and Neptune and
their global composition.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
R. A. Leske R. A. Mewaldt C. M. S. Cohen A. C. Cummings E. C. Stone M. E. Wiedenbeck T. T. von Rosenvinge 《Space Science Reviews》2007,130(1-4):335-340
Measurements below several MeV/nucleon from Wind/LEMT and ACE/ULEIS show that elements heavier than Zn (Z=30) can be enhanced by factors of ∼100 to 1000, depending on species, in 3He-rich solar energetic particle (SEP) events. Using the Solar Isotope Spectrometer (SIS) on ACE we find that even large SEP
(LSEP) shock-accelerated events at energies from ∼10 to >100 MeV/nucleon are often very iron rich and might contain admixtures
of flare seed material. Studies of ultra-heavy (UH) SEPs (with Z>30) above 10 MeV/nucleon can be used to test models of acceleration and abundance enhancements in both LSEP and 3He-rich events. We find that the long-term average composition for elements from Z=30 to 40 is similar to standard solar system values, but there is considerable event-to-event variability. Although most
of the UH fluence arrives during LSEP events, UH abundances are relatively more enhanced in 3He-rich events, with the (34<Z<40)/O ratio on average more than 50 times higher in 3He-rich events than in LSEP events. At energies >10 MeV/nucleon, the most extreme event in terms of UH composition detected
so far took place on 23 July 2004 and had a (34<Z<40)/O enhancement of ∼250–300 times the standard solar value. 相似文献
17.
R. A. Leske R. A. Mewaldt C. M. S. Cohen A. C. Cummings E. C. Stone M. E. Wiedenbeck T. T. von Rosenvinge 《Space Science Reviews》2007,130(1-4):195-205
Solar energetic particles (SEPs) provide a sample of the Sun from which solar composition may be determined. Using high-resolution
measurements from the Solar Isotope Spectrometer (SIS) onboard NASA’s Advanced Composition Explorer (ACE) spacecraft, we have
studied the isotopic composition of SEPs at energies ≥20 MeV/nucleon in large SEP events. We present SEP isotope measurements
of C, O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni made in 49 large events from late 1997 to the present. The isotopic composition
is highly variable from one SEP event to another due to variations in seed particle composition or due to mass fractionation
that occurs during the acceleration and/or transport of these particles. We show that various isotopic and elemental enhancements
are correlated with each other, discuss the empirical corrections used to account for the compositional variability, and obtain
estimated solar isotopic abundances. We compare the solar values and their uncertainties inferred from SEPs with solar wind
and other solar system abundances and find generally good agreement. 相似文献
18.
John F. Kerridge 《Space Science Reviews》1977,20(1):3-68
Determinations of the abundances of iron and related elements in the photosphere, chromosphere and corona of the Sun and in solar and galactic cosmic rays are reviewed and compared with abundances derived from meteoritic data. Observed Solar System abundances are found to be in accord with predictions of nucleosynthesis under either hydrostatic or explosive conditions but cannot yet be used to define these processes uniquely.Distribution of iron among planets and meteorites can probably be adequately modelled by condensation and fractionation under equilibrium conditions above about 700 K but below that temperature it is likely that inhibited solid state diffusion perturbed attainment of equilibrium. Pertinent factors which are presently unknown include the mechanism responsible for metal-silicate fractionation, the grain size achieved by metallic iron in the nebula and whether iron-bearing silicate formed prior to accretion.Dedicated to Professor Harold C. UreyPublication Number 1560-Institute of Geophysics and Planetary Physics, University of California, Los Angeles. 相似文献
19.
Following on from IRAS, ISO has provided a huge advancement in our knowledge of the phenomenology of the infrared (IR) emission
of normal galaxies and the underlying physical processes. Highlights include the discovery of an extended cold dust emission
component, present in all types of gas-rich galaxies and carrying the bulk of the dust luminosity; the definitive characterisation
of the spectral energy distribution in the IR, revealing the channels through which stars power the IR light; the derivation
of realistic geometries for stars and dust from ISO imaging; the discovery of cold dust associated with H I extending beyond the optical body of galaxies; the remarkable similarity of the near-IR (NIR)/mid-IR (MIR) SEDs for spiral
galaxies, revealing the importance of the photo-dissociation regions in the energy budget for that wavelength range; the importance
of the emission from the central regions in shaping up the intensity and the colour of the global MIR luminosity; the discovery
of the “hot” NIR continuum emission component of interstellar dust; the predominance of the diffuse cold neutral medium as
the origin for the main interstellar cooling line, [C II] 158 μm, in normal galaxies.
Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries:
France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA. 相似文献
20.
Observations carried out from the coronagraphs on board space missions (LASCO/SOHO, Solar Maximum and Skylab) and ground-based facilities (HAO/Mauna Loa Observatory) show that coronal mass ejections
(CMEs) can be classified into two classes based on their kinematics evolution. These two classes of CMEs are so-called fast
and slow CMEs. The fast CME starts with a high initial speed that remains more or less constant; it is also called the constant-speed CME. On the other hand, the slow CME starts with a low initial speed, but shows a gradual acceleration; it is also called
the accelerated and slow CME. Low and Zhang [Astrophys. J. 564, L53–L56, 2002] suggested that these two classes of CMEs could be a result of a difference in the initial topology of the
magnetic fields associated with the underlying quiescent prominences. A normal prominence magnetic field topology will lead
to a fast CME, while an inverse quiescent prominence results in a slow CME, because of the nature of the magnetic reconnection
processes. In a recent study given by Wu et al. [Solar Phys. 225, 157–175, 2004], it was shown that an inverse quiescent prominence magnetic topology also could produce a fast CME. In this
study, we perform a numerical MHD simulation for CMEs occurring in both normal and inverse quiescent prominence magnetic topology.
This study demonstrates three major physical processes responsible for destabilization of these two types of prominence magnetic
field topologies that can launch CMEs. These three initiation processes are identical to those used by Wu et al. [Solar Phys. 225, 157–175, 2004]. The simulations show that both fast and slow CMEs can be initiated from these two different types of magnetic
topologies. However, the normal quiescent prominence magnetic topology does show the possibility for launching a reconnection island (or secondary O-line) that might be thought of as a “CME’’. 相似文献