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1.
Luu  Jane  Lacerda  Pedro 《Earth, Moon, and Planets》2003,92(1-4):221-232
If we assume that the periodic brightness variations ina Kuiper Belt lightcurve are determined only by theiraspherical shapes and the observing geomtry, the fractionof detectable Kuiper Belt lightcurves and the lightcurveamplitude distribution can be used to constrain the shapesof Kuiper Belt objects. The results indicate that most KuiperBelt objects (～85%) have shapes that are close to spherical(a/b ≤ 1.5$), but there is a small but significant fraction(～12%) possessing highly aspherical shapes (a/b ≥ 1.7).The distribution cannot be well fitted by a gaussian and is betterapproximated by a power law.  相似文献   

2.
The Kuiper Belt zone is unique insofar as the major heat sources of objects a few tens of kilometers in size—solar radiation on the one hand and radioactive decay on the other—have comparable power. This leads to unique evolutionary patterns, with heat waves propagating inward from the irradiated surface and outward from the radioactively heated interior. A major radioactive source that is considered in this study is 26Al. The long-term evolution of several models with characteristics typical of Kuiper Belt objects is followed by means of a 1-D numerical code that solves the heat and mass balance equations on a spherically symmetric grid. The free parameters considered are radius (10-500 km), heliocentric distance (30-120 AU), and initial 26Al content (0-5×10−8 by mass). The initial composition assumed is a porous mixture of ices (H2O, CO, and CO2) and dust. Gases released in the interior are allowed to escape to the surface. It is shown that, depending on parameters, the interior may reach quite high temperatures (up to 180 K). The models suggest that Kuiper Belt objects are likely to lose the ices of very volatile species during early evolution; ices of less volatile species are retained in a surface layer, about 1 km thick. The models indicate that the amorphous ice crystallizes in the interior, and hence some objects may also lose part of the volatiles trapped in amorphous ice. Generally, the outer layers are far less affected than the inner part, resulting in a stratified composition and altered porosity distribution. These changes in structure and composition should have significant consequences for the short-period comets, which are believed to be descendants of Kuiper Belt objects.  相似文献   

3.
Neptune dominates the dynamics of the Kuiper Belt. By examining images of debris disks around other stars, we may be able to infer what kinds of planets shape the outer edges of other planetary systems. The last few years have seen a burst of progress in the modeling of azimuthal structures in debris disks created by planetary perturbers; new models incorporate planets on substantially eccentric orbits. I review this recent progress in debris disk dynamics and discuss the Kuiper Belt as a key example.  相似文献   

4.
We have been systematically monitoring a large sample of bright Kuiper Beltobjects for possible light variations due to rotational and phase angle effects.Here we report on three objects, 2003 AZ84, (24835) 1995 SM55and (55636) 2002 TX300 observed to have measurable rotational lightcurveswith peak-to-peak amplitudes of 0.14 ± 0.03, 0.19 ± 0.05 and 0.08 ± 0.02magnitudes and single-peaked periods of 6.71 ± 0.05, 4.04 ± 0.03 and8.12 ± 0.08 hours, respectively. We observed a further ten objects whichshowed no rotational photometric variation within measurement uncertainties.In addition, we find that the lightcurve of 1995 SM55 may have a variableamplitude. We discuss this peculiar object as well as our observations of the reportedlyvariable Kuiper Belt object (19308) 1996 TO66. Finally, we continue to find the phase functions of the Kuiper Belt objects to be very steep and linear, to firstorder, with a median slope of 0.16 ± 0.01 magnitudes per degree in the phaseangle range 0 to 2 degrees.  相似文献   

5.
Recent observations indicate that >99% of the small bodies in the solar system reside in its outer reaches—in the Kuiper Belt and Oort Cloud. Kuiper Belt bodies are probably the best‐preserved representatives of the icy planetesimals that dominated the bulk of the solid mass in the early solar system. They likely contain preserved materials inherited from the protosolar cloud, held in cryogenic storage since the formation of the solar system. Despite their importance, they are relatively underrepresented in our extraterrestrial sample collections by many orders of magnitude (~1013 by mass) as compared with the asteroids, represented by meteorites, which are composed of materials that have generally been strongly altered by thermal and aqueous processes. We have only begun to scratch the surface in understanding Kuiper Belt objects, but it is already clear that the very limited samples of them that we have in our laboratories hold the promise of dramatically expanding our understanding of the formation of the solar system. Stardust returned the first samples from a known small solar system body, the Jupiter‐family comet 81P/Wild 2, and, in a separate collector, the first solid samples from the local interstellar medium. The first decade of Stardust research resulted in more than 142 peer‐reviewed publications, including 15 papers in Science. Analyses of these amazing samples continue to yield unexpected discoveries and to raise new questions about the history of the early solar system. We identify nine high‐priority scientific objectives for future Stardust analyses that address important unsolved problems in planetary science.  相似文献   

6.
Abstract— In the primordial solar system, the most plausible sources of the water accreted by the Earth were in the outer asteroid belt, in the giant planet regions, and in the Kuiper Belt. We investigate the implications on the origin of Earth's water of dynamical models of primordial evolution of solar system bodies and check them with respect to chemical constraints. We find that it is plausible that the Earth accreted water all along its formation, from the early phases when the solar nebula was still present to the late stages of gas‐free sweepup of scattered planetesimals. Asteroids and the comets from the Jupiter‐Saturn region were the first water deliverers, when the Earth was less than half its present mass. The bulk of the water presently on Earth was carried by a few planetary embryos, originally formed in the outer asteroid belt and accreted by the Earth at the final stage of its formation. Finally, a late veneer, accounting for at most 10% of the present water mass, occurred due to comets from the Uranus‐Neptune region and from the Kuiper Belt. The net result of accretion from these several reservoirs is that the water on Earth had essentially the D/H ratio typical of the water condensed in the outer asteroid belt. This is in agreement with the observation that the D/H ratio in the oceans is very close to the mean value of the D/H ratio of the water inclusions in carbonaceous chondrites.  相似文献   

7.
The spectra of water ice on the surfaces of icy satellites and Kuiper Belt Objects (KBOs) indicate that the surface ice on these bodies is in a crystalline state. This conflicts with theoretical models, which predict that radiation (galactic cosmic rays and solar ultraviolet) should damage the crystalline structure of ice on geologically short timescales. Temperatures are too low in the outer Solar System for the ice to anneal, and reflectance spectra of these bodies should match those of amorphous solid water (ASW). We assess whether the kinetic energy deposited as heat by micrometeorite impacts on outer Solar System bodies is sufficient to anneal their surface ice down to a near-infrared optical depth . We calculate the kinetic energy flux from interplanetary micrometeorite impacts, including gravitational focusing. We also calculate the thermal diffusion of impact heat in various surfaces and the rate of annealing of ice. We conclude that the rate of annealing from micrometeorite impacts is sufficient to explain the crystallinity of ice on nearly all the surfaces of the saturnian, uranian and neptunian satellites. We discuss how the model can be used in conjunction with spectra of KBOs to probe dust fluxes in the Kuiper Belt.  相似文献   

8.
We present new visible-infrared (V−J) observations of 17 Kuiper Belt objects, of which 14 were observed in the visible and infrared wavebands simultaneously to limit the effects of lightcurve variations. Combining these data with our previously published visible-infrared data provides a dataset of 29 objects, 25 of which offer simultaneous V−J colors. We examine the resulting dataset for evidence of relationships between physical properties and orbital characteristics. We find no evidence of a color-size relationship (as previously suspected), at least over the size range sampled. The dataset supports the trend, reported elsewhere, that there is a predominance of red material on the surfaces of objects having perihelia beyond 40 AU. Our data are also supportive, albeit weakly, of a reported correlation between inclination and color in the classical Kuiper Belt — although it is perhaps more correct to say that our data show that there appears to be a lack of low inclination blue objects. Our V−J colors appear broadly correlated with published optical colors, thus suggesting that the surfaces of Kuiper Belt objects are subject to a single reddening agent.  相似文献   

9.
We have measured near-infrared colorsof the binary Kuiper Belt object (KBO)1998 WW31 using the Subaru Telescope withadaptive optics. The satellite was detectednear its perigee and apogee(0.18“ and 1.2” apart from the primary).The primary and the satellite have similar H–Kcolors, while the satellite is redder thanthe primary in J–H. Combined with the Rband magnitude previously published byVeillet et al., 2002, the color of the primaryis consistent with that of optically red KBOs. Thesatellite's R-, J-, H-colors suggest thepresence of ～1 μm absorption band dueto rock-forming minerals. If the surface of thesatellite is mainly composed by olivine, thesatellite's albedo is higher value than the canonicallyassumed value of 4%.  相似文献   

10.
In this paper we determine dynamically the mass of the Kuiper Belt Objects by exploiting the latest least-squares determinations of the extra rates of perihelia of the inner planets of the Solar system. By modelling classical Kuiper Belt Objects as an ecliptic ring of finite thickness, we obtain 0.033 ± 0.115 in units of terrestrial masses. For resonant Kuiper Belt Objects, a two-ring model yields 0.018 ± 0.063. These values are consistent with recent determinations obtained using ground- and space-based optical techniques. Some implications for precise tests of Einsteinian and post-Einsteinian gravity are briefly discussed.  相似文献   

11.
Many nearby main sequence stars are surrounded by cool dust radiating strongly in the far-IR. The characteristics of some of the prototype systems will be discussed. The dust is understood to represent debris related to planet formation, and the known disk systems may be dense analogs of the Kuiper Belt structure in our outer solar system. ISO observing programs plan to address questions regarding how common planetary material is around normal stars and how its amount and location depend on system age. These questions are central to an understanding of the place of the "Vega/β Pic" disks in stellar evolution. Preliminary results from the first year of ISO operation will be reported. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

12.
《Icarus》2003,166(1):195-211
We present optical observations of 24 Centaurs performed between 1998 and 2002 with the University of Hawaii 2.2-m telescope. This is the largest such Centaur survey to date. We report colors for all objects, and show that they cover a continuum with mean V–R color of 0.58±0.01 and standard deviation 0.15. The color distribution fits between those of the Kuiper Belt and the cometary nuclei, and seems consistent with the dynamical concept of the majority of Centaurs originating from the Kuiper Belt. We find no strong correlation between a Centaur's color and its orbital elements; there is at best a <3−σ correlation with semimajor axis, with redder Centaurs being farther from the Sun. We have calculated the phase-darkening slope parameters G for 5 Centaurs, 4 of which are reported for the first time. They range from −0.18 to 0.13. We have sufficient data to constrain the rotation periods of two Centaurs, 1999 UG5 (which we reported earlier) and 1998 SG35. We performed a comparison of the surface brightness profiles of 10 apparently-inactive Centaurs with point sources. We found no coma around these 10 objects, including C/LINEAR (2000 B4), and generally the upper limits to the dust mass loss rates are below 0.05 kg s−1.  相似文献   

13.
New Horizons: The First Reconnaissance Mission to Bodies in the Kuiper Belt   总被引：1，自引：0，他引：1  
Stern  Alan  Spencer  John 《Earth, Moon, and Planets》2003,92(1-4):477-482
NASA has long been planning a mission of exploration to Pluto-Charon and the Kuiper Belt (e.g., Terrile et al., 1997). In 2001 NASA selected such a mission (NASA, 2001), called New Horizons, for design and development. New Horizons is now funded and planning a launch in January 2006. The mission plans to carry 8 scientific sensors and make flybys of Pluto-Charon and one or more KBOs. Statistical Monte Carlo simulations indicate that New Horizons has sufficient fuel to reach one or more KBOs with diameters exceeding 35 km. If launched as planned in 2006, the mission will use a Jovian gravity assist, arriving at Pluto-Charon in 2015 or 2016; if launched in its backup window in 2007, a Jovian gravity assist is not feasible and arrival will be later – 2019. Below we briefly summarize the New Horizons mission, concentrating on its role in Kuiper Belt exploration.  相似文献   

14.
Numerical integrations of the four major planets orbits inside a primordialplanetesimals disk show that a fraction of Neptune primordial scatteredobjects are deposited into the classical Kuiper Belt at Solar System age. Theseobjects exhibit inclinations as high as 40° and can account forpresent high inclinations population in the classical Kuiper Belt. The samemechanism can also originate high perihelion scattered objects like 2000 CR105. The process that in the end produced such objects can be divided into two phases, a migration phase where nonconservative dynamics acted to producesome stable objects already at 108 years and a nonmigrating phase that helped to establish some other objects as stable TNO's. Low inclination CKBO's have inprinciple an origin through the resonance sweeping process, although someresults from numerical integrations at least suggest a possible origin also fromthe primordial Neptune scattered population.  相似文献   

15.
One of the main particular features of the structure of the Kuiper Belt is that it contains clusters of objects of small orbital eccentricity and inclination (“cold population”). In order to solve the problem of the origin of the objects, we considered the process of the gravitational interaction of a comparatively small-mass planet with a planetesimal disk. We found that one particular property of the process is that the planet changes its direction of migration. The interaction with the planet results in the transportation of a considerable portion of planetesimals from the inner zone out to the Kuiper Belt. After such a transition of the objects, the planet returns to the inner regions of the planetesimal disk. Numerical simulations show that the reversible migration of a planet of a mass similar to that of the Earth can explain the main properties of the Kuiper Belt’s cold population orbit distribution.  相似文献   

16.
We have been awarded NASA Key Project observing time on ISO, in order to establish the true frequency of far-infrared excesses in a volume-limited sample of main sequence and related stars, and address the relative success or failure of single stars in processes related to the forming of planetary systems. For a volume-limited subset of main sequence and related stars, PHT03 measurements at 3.6, 11.5, 20 and 60 micron will be obtained, using a 120 arsec aperture in all cases to eliminate possible companion confusion with differing apertures, to ascertain spectral energy distributions. For the M dwarfs, 100 micron observations will also be obtained. For some, brighter sources, more extensive wavelength coverage and improved spatial resolution will be attempted, using CAM and SWS. Spatially over-sampled PHOT observations will be made at 60 micron of the brightest and nearest Vega-like sources to measure the characteristic sizes of the emitting regions and obtain some information regarding their shapes and orientations. The goal is not a map, but scan profiles along 3 position angles which can be deconvolved to find the intrinsic size and shape of the half-maximum contour of the emitting region. Photometry of selected lines of sight through the zodiacal dust will also be carried out to look for outer solar system (Kuiper Belt) material. Observation at a range of wavelengths, ecliptic latitudes and at 2 epochs is designed to help untangle foreground Zodiacal from background Kuiper flux, not necessarily to look for individual macroscopic objects.  相似文献   

17.
By telescopic tracking, we have established that the transneptunian object (TNO) 2000 CR105 has a semimajor axis of 220±1 AU and perihelion distance of 44.14±0.02 AU, beyond the domain which has heretofore been associated with the “scattered disk” of Kuiper Belt objects interacting via gravitational encounters with Neptune. We have also firmly established that the TNO 1995 TL8 has a high perihelion (of 40.08±0.02 AU). These objects, and two other recent discoveries which appear to have perihelia outside 40 AU, have probably been placed on these orbits by a gravitational interaction which is not strong gravitational scattering off of any of the giant planets on their current orbits. Their existence may thus have profound cosmogonic implications for our understanding of the formation of the outer Solar System. We discuss some viable scenarios which could have produced these objects, including long-term diffusive chaos and scattering off of other massive bodies in the outer Solar System. This discovery implies that there must be a large population of TNOs in an “extended scattered disk” with perihelia above the previously suggested 38 AU boundary. The total population is difficult to estimate due to the ease with which such objects would have been lost. This illustrates the great value of frequent and well time-sampled recovery observations of trans-neptunian objects within their discovery opposition.  相似文献   

18.
Osip  David J.  Kern  S. D.  Elliot  J. L. 《Earth, Moon, and Planets》2003,92(1-4):409-421
Following our discovery of 2001 QT297 as the second knownbinary Edgeworth–Kuiper Belt Object (EKBO) in October of 2001 [IAUC 7733], we havecarried out additional high spatial resolution ground based imaging in October andNovember of 2001 and July, August, and September of 2002. Using the Raymond andBeverly Sackler Magellan Instant Camera (MagIC) on the Baade and Clay 6.5 m telescopesat Las Campanas Observatory in Chile, we have obtained accurate astrometric and photometricmeasurements in the Sloan r’ i’ and g’ filters. Superb seeing conditions andPSF fitting allow an accurate determination of the binary component separation and positionangle over time as well as a detailed study of color and temporal variability of the individualcomponents. Here we present a physical characterization of the individual componentsof 2001 QT297 based on these astrometric, color and variability measurements. We findthe primary to exhibit colors about 0.3 magnitudes redder than solar with no evidencefor variability. The secondary component, however, exhibits strong variability(～0.6 magnitudes) with a best fit period of 4.7526 ± 0.0007 h for a single peaklightcurve or 9.505 ± 0.001 h for a dual peaked lightcurve. The colors measured for thesecondary also suggest variability. Based on a preliminary orbit fit for thepair using observations spanning a one year arc, we are able to estimate a system mass of～ 3.2 × 1018 kg and provide constraints to the surface albedo of 9–14% for assumeddensities between 1 and 2 g/cm3.  相似文献   

19.
Fast photometric observations of target stars in the ecliptic are a powerful tool to detect small objects in the Kuiper Belt. The various parameters involved in such observations are described. Meter-sized telescopes are able to detect sub-kilometer KBO (Kuiper Belt Objects). A campaign of research of KBO by stellar occultations, organized at the Pic du Midi Observatory is presented. These observations bring the first constraint on the small end of the size distribution of the KBOs.  相似文献   

20.
We discuss the structure of the Kuiper belt as it can be inferred from the first decade of observations. In particular, we focus on its most intriguing properties – the mass deficit, inclination distribution, the apparent existence of an outer edge and of a correlation among inclinations, colours and sizes – which clearly show that the belt has lost its pristine structureof a dynamically cold proto-planetary disk. Understanding how the Kuiperbelt acquired its present structure will provide insight into the formationof the outer planetary system and on its early evolution. We outline ascenario of primordial sculpting – issued from a combination of mechanismsproposed by various authors – that seems to explain most of the observedproperties of the Kuiper belt. Several aspects are not yet totallyclear. But, for the first time, we have a view – if not of the detailedsculpture – at least of its rough cast.  相似文献   

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