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Michael E Brown - One of the best experts on this subject based on the ideXlab platform.
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injection of inner oort cloud objects into the distant Kuiper Belt by planet nine
arXiv: Earth and Planetary Astrophysics, 2021Co-Authors: Konstantin Batygin, Michael E BrownAbstract:The outer solar system exhibits an anomalous pattern of orbital clustering, characterized by an approximate alignment of the apsidal lines and angular momentum vectors of distant, long-term stable Kuiper Belt objects. One explanation for this dynamical confinement is the existence of a yet-undetected planetary-mass object, "Planet Nine (P9)". Previous work has shown that trans-Neptunian objects, which originate within the scattered disk population of the Kuiper Belt, can be corralled into orbital alignment by Planet Nine's gravity over ~Gyr timescales, and characteristic P9 parameters have been derived by matching the properties of a synthetic Kuiper Belt generated within numerical simulations to the available observational data. In this work, we show that an additional dynamical process is in play within the framework of the Planet Nine hypothesis, and demonstrate that P9-induced dynamical evolution facilitates orbital variations within the otherwise dynamically frozen inner Oort cloud. As a result of this evolution, inner Oort cloud bodies can acquire orbits characteristic of the distant scattered disk, implying that if Planet Nine exists, the observed census of long-period trans-Neptunian objects is comprised of a mixture of Oort cloud and Kuiper Belt objects. Our simulations further show that although inward-injected inner Oort cloud objects exhibit P9-driven orbital confinement, the degree of clustering is weaker than that of objects originating within the Kuiper Belt. Cumulatively, our results suggest that a more eccentric Planet Nine is likely necessary to explain the data than previously thought.
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Medium-sized satellites of large Kuiper Belt objects
The Astronomical Journal, 2018Co-Authors: Michael E Brown, Bryan J. ButlerAbstract:While satellites of mid- to small-Kuiper Belt objects tend to be similar in size and brightness to their primaries, the largest Kuiper Belt objects preferentially have satellites with small fractional brightness. In the two cases where the sizes and albedos of the small faint satellites have been measured, these satellites are seen to be small icy fragments consistent with collisional formation. Here we examine Dysnomia and Vanth, the satellites of Eris and Orcus, respectively. Using the Atacama Large Millimeter Array, we obtain the first spatially resolved observations of these systems at thermal wavelengths. We find a diameter for Dysnomia of 700+/-115 km and for Vanth of 475+/-75 km, with albedos of 0.04_+0.02_-0.01 and 0.08+/-0.02 respectively. Both Dysnomia and Vanth are indistinguishable from typical Kuiper Belt objects of their size. Potential implications for the formation of these types of satellites are discussed.
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the generation of the distant Kuiper Belt by planet nine from an initially broad perihelion distribution
arXiv: Earth and Planetary Astrophysics, 2018Co-Authors: Tali Khain, Konstantin Batygin, Michael E BrownAbstract:The observation that the orbits of long-period Kuiper Belt objects are anomalously clustered in physical space has recently prompted the Planet Nine hypothesis - the proposed existence of a distant and eccentric planetary member of our solar system. Within the framework of this model, a Neptune-like perturber sculpts the orbital distribution of distant Kuiper Belt objects through a complex interplay of resonant and secular effects, such that in addition to perihelion-circulating objects, the surviving orbits get organized into apsidally aligned and anti-aligned configurations with respect to Planet Nine's orbit. In this work, we investigate the role of Kuiper Belt initial conditions on the evolution of the outer solar system using numerical simulations. Intriguingly, we find that the final perihelion distance distribution depends strongly on the primordial state of the system, and demonstrate that a bimodal structure corresponding to the existence of both aligned and anti-aligned clusters is only reproduced if the initial perihelion distribution is assumed to extend well beyond $\sim 36$ AU. The bimodality in the final perihelion distance distribution is due to the existence of permanently stable objects, with the lower perihelion peak corresponding to the anti-aligned orbits and the higher perihelion peak corresponding to the aligned orbits. We identify the mechanisms which enable the persistent stability of these objects and locate the regions of phase space in which they reside. The obtained results contextualize the Planet Nine hypothesis within the broader narrative of solar system formation, and offer further insight into the observational search for Planet Nine.
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2004 ew95 a phyllosilicate bearing carbonaceous asteroid in the Kuiper Belt
The Astrophysical Journal, 2018Co-Authors: Tom Seccull, Michael E Brown, Wesley C Fraser, Thomas H Puzia, F SchonebeckAbstract:Models of the Solar System's dynamical evolution predict the dispersal of primitive planetesimals from their formative regions among the gas-giant planets due to the early phases of planetary migration. Consequently, carbonaceous objects were scattered both into the outer asteroid Belt and out to the Kuiper Belt. These models predict that the Kuiper Belt should contain a small fraction of objects with carbonaceous surfaces, though to date, all reported visible reflectance spectra of small Kuiper Belt Objects (KBOs) are linear and featureless. We report the unusual reflectance spectrum of a small KBO, (120216) 2004 EW_(95), exhibiting a large drop in its near-UV reflectance and a broad shallow optical absorption feature centered at ~700 nm, which is detected at greater than 4σ significance. These features, confirmed through multiple epochs of spectral photometry and spectroscopy, have respectively been associated with ferric oxides and phyllosilicates. The spectrum bears striking resemblance to those of some C-type asteroids, suggesting that 2004 EW_(95) may share a common origin with those objects. 2004 EW95 orbits the Sun in a stable mean motion resonance with Neptune, at relatively high eccentricity and inclination, suggesting it may have been emplaced there by some past dynamical instability. These results appear consistent with the aforementioned model predictions and are the first to show a reliably confirmed detection of silicate material on a small KBO.
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the density of mid sized Kuiper Belt object 2002 ux25 and the formation of the dwarf planets
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Michael E BrownAbstract:The formation of the largest objects in the Kuiper Belt, with measured densities of ~1.5 g cm-3 and higher, from the coagulation of small bodies, with measured densities below 1 g cm-3 is difficult to explain without invoking significant porosity in the smallest objects. If such porosity does occur, measured densities should begin to increase at the size at which significant porosity is no longer supported. Among the asteroids, this transition occurs for diameters larger than ~350 km. In the Kuiper Belt, no density measurements have been made between ~350 km and ~850 km, the diameter range where porosities might first begin to drop. Objects in this range could provide key tests of the rock fraction of small Kuiper Belt objects. Here we report the orbital characterization, mass, and density determination of the 2002 UX25 system in the Kuiper Belt. For this object, with a diameter of ~650 km, we find a density of 0.82+/-0.11 g cm-3, making it the largest solid known object in the solar system with a measured density below that of pure water ice. We argue that the porosity of this object is unlikely to be above ~20%, suggesting a low rock fraction. If the currently measured densities of Kuiper Belt objects are a fair representation of the sample as a whole, creating ~1000 km and larger Kuiper Belt objects with rock mass fractions of 70% and higher from coagulation of small objects with rock fractions as low as those inferred from 2002 UX25 is difficult.
Jane Luu - One of the best experts on this subject based on the ideXlab platform.
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crystalline water ice on the Kuiper Belt object 50000 quaoar
Nature, 2004Co-Authors: David Jewitt, Jane LuuAbstract:The Kuiper Belt is a disk-like structure consisting of solid bodies orbiting the Sun beyond Neptune1. It is the source of the short-period comets and the likely repository of the Solar System's most primitive materials2. Surface temperatures in the Belt are low (∼ 50 K), suggesting that ices trapped at formation should have been preserved over the age of the Solar System. Unfortunately, most Kuiper Belt objects are too faint for meaningful compositional study, even with the largest available telescopes. Water ice has been reported in a handful of objects3,4,5, but most appear spectrally featureless5,6. Here we report near-infrared observations of the large Kuiper Belt object (50000) Quaoar, which reveal the presence of crystalline water ice and ammonia hydrate. Crystallinity indicates that the ice has been heated to at least 110 K. Both ammonia hydrate and crystalline water ice should be destroyed by energetic particle irradiation on a timescale of about 107 yr. We conclude that Quaoar has been recently resurfaced, either by impact exposure of previously buried (shielded) ices or by cryovolcanic outgassing, or by a combination of these processes.
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optical and infrared reflectance spectrum of Kuiper Belt object 1996 tl66
The Astrophysical Journal, 1998Co-Authors: Jane Luu, David JewittAbstract:We have obtained optical (0.4-0.8 μm) and near-infrared (1.0-2.5 μm) reflectance spectra of the Kuiper Belt object 1996 TL66. The spectra show no evidence for absorption features and are neutral across the full wavelength range. The spectrum of TL66 is thus similar to that of the Centaur Chiron but different from that of the Centaur Pholus. It also bears no resemblance to the spectrum of the Kuiper Belt object 1993 SC reported by Brown et al. (1997).
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discovery of the candidate Kuiper Belt object 1992 qb1
Nature, 1993Co-Authors: David Jewitt, Jane LuuAbstract:The discovery of a new faint object in the outer solar system, 1992 QB1, moving beyond the orbit of Neptune is reported. It is suggested that the 1992 QB1 may represent the first detection of a member of the Kuiper Belt (Edgworth, 1949; Kuiper, 1951), the hypothesized population of objects beyond Neptune and a possible source of the short-period comets, as suggested by Whipple (1964), Fernandez (1980), and Duncan et al. (1988).
David Jewitt - One of the best experts on this subject based on the ideXlab platform.
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crystalline water ice on the Kuiper Belt object 50000 quaoar
Nature, 2004Co-Authors: David Jewitt, Jane LuuAbstract:The Kuiper Belt is a disk-like structure consisting of solid bodies orbiting the Sun beyond Neptune1. It is the source of the short-period comets and the likely repository of the Solar System's most primitive materials2. Surface temperatures in the Belt are low (∼ 50 K), suggesting that ices trapped at formation should have been preserved over the age of the Solar System. Unfortunately, most Kuiper Belt objects are too faint for meaningful compositional study, even with the largest available telescopes. Water ice has been reported in a handful of objects3,4,5, but most appear spectrally featureless5,6. Here we report near-infrared observations of the large Kuiper Belt object (50000) Quaoar, which reveal the presence of crystalline water ice and ammonia hydrate. Crystallinity indicates that the ice has been heated to at least 110 K. Both ammonia hydrate and crystalline water ice should be destroyed by energetic particle irradiation on a timescale of about 107 yr. We conclude that Quaoar has been recently resurfaced, either by impact exposure of previously buried (shielded) ices or by cryovolcanic outgassing, or by a combination of these processes.
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optical and infrared reflectance spectrum of Kuiper Belt object 1996 tl66
The Astrophysical Journal, 1998Co-Authors: Jane Luu, David JewittAbstract:We have obtained optical (0.4-0.8 μm) and near-infrared (1.0-2.5 μm) reflectance spectra of the Kuiper Belt object 1996 TL66. The spectra show no evidence for absorption features and are neutral across the full wavelength range. The spectrum of TL66 is thus similar to that of the Centaur Chiron but different from that of the Centaur Pholus. It also bears no resemblance to the spectrum of the Kuiper Belt object 1993 SC reported by Brown et al. (1997).
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discovery of the candidate Kuiper Belt object 1992 qb1
Nature, 1993Co-Authors: David Jewitt, Jane LuuAbstract:The discovery of a new faint object in the outer solar system, 1992 QB1, moving beyond the orbit of Neptune is reported. It is suggested that the 1992 QB1 may represent the first detection of a member of the Kuiper Belt (Edgworth, 1949; Kuiper, 1951), the hypothesized population of objects beyond Neptune and a possible source of the short-period comets, as suggested by Whipple (1964), Fernandez (1980), and Duncan et al. (1988).
Wesley C Fraser - One of the best experts on this subject based on the ideXlab platform.
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2004 ew95 a phyllosilicate bearing carbonaceous asteroid in the Kuiper Belt
The Astrophysical Journal, 2018Co-Authors: Tom Seccull, Michael E Brown, Wesley C Fraser, Thomas H Puzia, F SchonebeckAbstract:Models of the Solar System's dynamical evolution predict the dispersal of primitive planetesimals from their formative regions among the gas-giant planets due to the early phases of planetary migration. Consequently, carbonaceous objects were scattered both into the outer asteroid Belt and out to the Kuiper Belt. These models predict that the Kuiper Belt should contain a small fraction of objects with carbonaceous surfaces, though to date, all reported visible reflectance spectra of small Kuiper Belt Objects (KBOs) are linear and featureless. We report the unusual reflectance spectrum of a small KBO, (120216) 2004 EW_(95), exhibiting a large drop in its near-UV reflectance and a broad shallow optical absorption feature centered at ~700 nm, which is detected at greater than 4σ significance. These features, confirmed through multiple epochs of spectral photometry and spectroscopy, have respectively been associated with ferric oxides and phyllosilicates. The spectrum bears striking resemblance to those of some C-type asteroids, suggesting that 2004 EW_(95) may share a common origin with those objects. 2004 EW95 orbits the Sun in a stable mean motion resonance with Neptune, at relatively high eccentricity and inclination, suggesting it may have been emplaced there by some past dynamical instability. These results appear consistent with the aforementioned model predictions and are the first to show a reliably confirmed detection of silicate material on a small KBO.
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all planetesimals born near the Kuiper Belt formed as binaries
Nature Astronomy, 2017Co-Authors: Wesley C Fraser, Kathryn Volk, David Nesvorný, J J Kavelaars, Michele T Bannister, Rosemary E Pike, Michael Marsset, Megan E Schwamb, Pedro Lacerda, A DelsantiAbstract:The discovery of several Kuiper Belt objects (KBOs) with anomalous properties (they are blue-coloured, whereas KBOs of the same type are red, and they are all binaries) gives constraints on formation processes in the outermost region of the Solar System.
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retention of a primordial cold classical Kuiper Belt in an instability driven model of solar system formation
The Astrophysical Journal, 2011Co-Authors: Konstantin Batygin, Michael E Brown, Wesley C FraserAbstract:The cold classical population of the Kuiper Belt exhibits a wide variety of unique physical characteristics, which collectively suggest that its dynamical coherence has been maintained throughout the solar system's lifetime. Simultaneously, the retention of the cold population's relatively unexcited orbital state has remained a mystery, especially in the context of a solar system formation model, that is driven by a transient period of instability, where Neptune is temporarily eccentric. Here, we show that the cold Belt can survive the instability, and its dynamical structure can be reproduced. We develop a simple analytical model for secular excitation of cold Kuiper Belt objects and show that comparatively fast apsidal precession and nodal recession of Neptune, during the eccentric phase, are essential for preservation of an unexcited state in the cold classical region. Subsequently, we confirm our results with self-consistent N-body simulations. We further show that contamination of the hot classical and scattered populations by objects of similar nature to that of cold classicals has been instrumental in shaping the vast physical diversity inherent to the Kuiper Belt.
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retention of a primordial cold classical Kuiper Belt in an instability driven model of solar system formation
arXiv: Earth and Planetary Astrophysics, 2011Co-Authors: Konstantin Batygin, Michael E Brown, Wesley C FraserAbstract:The cold classical population of the Kuiper Belt exhibits a wide variety of unique physical characteristics, which collectively suggest that its dynamical coherence has been maintained through out the solar system's lifetime. Simultaneously, the retention of the cold population's relatively unexcited orbital state has remained a mystery, especially in the context of a solar system formation model, that is driven by a transient period of instability, where Neptune is temporarily eccentric. Here, we show that the cold Belt can survive the instability, and its dynamical structure can be reproduced. We develop a simple analytical model for secular excitation of cold KBOs and show that comparatively fast apsidal precession and nodal recession of Neptune, during the eccentric phase, are essential for preservation of an unexcited state in the cold classical region. Subsequently, we confirm our results with self-consistent N-body simulations. We further show that contamination of the hot classical and scattered populations by objects of similar nature to that of cold classicals has been instrumental in shaping the vast physical diversity inherent to the Kuiper Belt.
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the luminosity function of the hot and cold Kuiper Belt populations
Icarus, 2010Co-Authors: Wesley C Fraser, Michael E Brown, Megan E SchwambAbstract:We have performed an ecliptic survey of the Kuiper Belt, with an areal coverage of 8.9 square degrees to a 50% limiting magnitude of r'_(Sloan) = 24.7, and have detected 88 Kuiper Belt objects, roughly half of which received follow-up 1–2 months after detection. Using this survey data alone, we have measured the luminosity function of the Kuiper Belt, thus avoiding any biases that might come from the inclusion of other observations. We have found that the Cold population defined as having inclinations less than 5° has a luminosity function slope α_(Cold) = 0.82 ± 0.23, and is different from the Hot population, which has inclinations greater than 5° and a luminosity function slope α_(Hot) = 0.35 ± 0.21. As well, we have found that those objects closer than 38 AU have virtually the same luminosity function slope as the Hot population. This result, along with similar findings of past surveys demonstrates that the dynamically Cold Kuiper Belt objects likely have a steep size distribution, and are unique from all of the excited populations which have much shallower distributions. This suggests that the dynamically excited population underwent a different accretion history and achieved a more evolved state of accretion than the Cold population. As well, we discuss the similarities of the Cold and Hot populations with the size distributions of other planetesimal populations. We find that while the Jupiter family comets and the scattered disk exhibit similar size distributions, a power-law extrapolation to small sizes for the scattered disk cannot account for the observed influx of comets. As well, we have found that the Jupiter Trojan and Hot populations cannot have originated from the same parent population, a result that is difficult to reconcile with scattering models similar to the NICE model. We conclude that the similarity between the size distributions of the Cold population and the Jupiter Trojan population is a striking coincidence.
Alessandro Morbidelli - One of the best experts on this subject based on the ideXlab platform.
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dynamical effects on the classical Kuiper Belt during the excited neptune model
Icarus, 2019Co-Authors: Alessandro Morbidelli, R S Gomes, Rafael Ribeiro De Sousa, Ernesto Vieira NetoAbstract:Abstract The link between the dynamical evolution of the giant planets and the Kuiper Belt orbital structure can provide clues and insight about the dynamical history of the Solar System. The classical region of the Kuiper Belt has two populations (the cold and hot populations) with completely different physical and dynamical properties. These properties have been explained in the framework of a sub-set of the simulations of the Nice Model, in which Neptune remained on a low-eccentricity orbit (Neptune’s eccentricity is never larger than 0.1) throughout the giant planet instability (Nesvorný 2015a,b). However, recent simulations (Gomes et al., 2018) have showed that the remaining Nice model simulations, in which Neptune temporarily acquires a large-eccentricity orbit (larger than 0.1), are also consistent with the preservation of the cold population (inclination smaller than 4°), if the latter formed in situ. However, the resulting a cold population showed in many of the simulations eccentricities larger than those observed for the real population. The purpose of this work is to discuss the dynamical effects on the Kuiper Belt region due to an excited Neptune phase. We focus on a short period of time, of about six hundred thousand years, which is characterized by Neptune’s large eccentricity and smooth migration with a slow precession of Neptune’s perihelion. This phase was observed during a full simulation of the Nice Model (Gomes et al., 2018) just after the last jump of Neptune’s orbit due to an encounter with another planet. We show that if self-gravity is considered in the disk, the precession rate of the particles longitude of perihelion ϖ is slowed down, which in turn speeds up the cycle of ϖ N − ϖ (the subscript N referring to Neptune), associated to the particles eccentricity evolution. This, combined with the effect of mutual scattering among the bodies, which spreads all orbital elements, allows some objects to return to low eccentricities. However, we show that if the cold population originally had a small total mass, this effect is negligible. Thus, we conclude that the only possibilities to keep at low eccentricity some cold-population objects during a high-eccentricity phase of Neptune are that (i) either Neptune’s precession was rapid, as suggested by Batygin et al. (2011) or (ii) Neptune’s slow precession phase was long enough to allow some particles to experience a full secular cycle of ϖ − ϖ N .
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origin of the structure of the Kuiper Belt during a dynamical instability in the orbits of uranus and neptune
Icarus, 2008Co-Authors: Harold F Levison, Alessandro Morbidelli, R S Gomes, Christa Vanlaerhoven, K TsiganisAbstract:Abstract We explore the origin and orbital evolution of the Kuiper Belt in the framework of a recent model of the dynamical evolution of the giant planets, sometimes known as the Nice model. This model is characterized by a short, but violent, instability phase, during which the planets were on large eccentricity orbits. It successfully explains, for the first time, the current orbital architecture of the giant planets [Tsiganis, K., Gomes, R., Morbidelli, A., Levison, H.F., 2005. Nature 435, 459–461], the existence of the Trojans populations of Jupiter and Neptune [Morbidelli, A., Levison, H.F., Tsiganis, K., Gomes, R., 2005. Nature 435, 462–465], and the origin of the late heavy bombardment of the terrestrial planets [Gomes, R., Levison, H.F., Tsiganis, K., Morbidelli, A., 2005. Nature 435, 466–469]. One characteristic of this model is that the proto-planetary disk must have been truncated at roughly 30 to 35 AU so that Neptune would stop migrating at its currently observed location. As a result, the Kuiper Belt would have initially been empty. In this paper we present a new dynamical mechanism which can deliver objects from the region interior to ∼ 35 AU to the Kuiper Belt without excessive inclination excitation. In particular, we show that during the phase when Neptune's eccentricity is large, the region interior to its 1:2 mean motion resonance becomes unstable and disk particles can diffuse into this area. In addition, we perform numerical simulations where the planets are forced to evolve using fictitious analytic forces, in a way consistent with the direct N -body simulations of the Nice model. Assuming that the last encounter with Uranus delivered Neptune onto a low-inclination orbit with a semi-major axis of ∼ 27 AU and an eccentricity of ∼0.3, and that subsequently Neptune's eccentricity damped in ∼1 My, our simulations reproduce the main observed properties of the Kuiper Belt at an unprecedented level. In particular, our results explain, at least qualitatively: (1) the co-existence of resonant and non-resonant populations, (2) the eccentricity–inclination distribution of the Plutinos, (3) the peculiar semi-major axis—eccentricity distribution in the classical Belt, (4) the outer edge at the 1:2 mean motion resonance with Neptune, (5) the bi-modal inclination distribution of the classical population, (6) the correlations between inclination and physical properties in the classical Kuiper Belt, and (7) the existence of the so-called extended scattered disk. Nevertheless, we observe in the simulations a deficit of nearly-circular objects in the classical Kuiper Belt.
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coupling dynamical and collisional evolution of small bodies ii forming the Kuiper Belt the scattered disk and the oort cloud
Icarus, 2007Co-Authors: Sebastien Charnoz, Alessandro MorbidelliAbstract:Abstract The Oort Cloud, the Kuiper Belt and the Scattered Disk are dynamically distinct populations of small bodies evolving in the outer regions of the Solar System. Whereas their collisional activity is now quiet, gravitational interactions with giant planets may have shaped these populations both dynamically and collisionally during their formation. Using a hybrid approach [Charnoz, S., Morbidelli, A., 2003. Icarus 166, 141–166], the present paper tries to couple the primordial collisional and dynamical evolution of these three populations in a self-consistent way. A critical parameter is the primordial size-distribution. We show that the initial planetesimal size distribution that allows an effective mass depletion of the Kuiper Belt by collisional grinding, would decimate also the population of comet-size bodies that end in the Oort Cloud and, in particular, in the Scattered Disk. As a consequence, the Oort Cloud and the Scattered Disk would be too anemic, by a factor 20 to 100, relative to the estimates achieved from the observation of the fluxes of long period and Jupiter family comets, respectively. For these two reservoirs to have a sufficient number of comets, the initial size distribution in the planetesimal disk had to be such that the mass depletion by collisional erosion of the Kuiper Belt was negligible. Consequently the current mass deficit of the Kuiper Belt needs to be explained by dynamical mechanisms.
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the Kuiper Belt and the primordial evolution of the solar system
Comets II, 2004Co-Authors: Alessandro Morbidelli, Michael E BrownAbstract: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, the inclination distribution, and the apparent existence of an outer edge and a correlation among inclinations, colors, and sizes — which clearly show that the Belt has lost the pristine structure of a dynamically cold protoplanetary disk. Understanding how the Kuiper Belt acquired its present structure will provide insight into the formation of the outer planetary system and its early evolution. We critically review the scenarios that have been proposed so far for the primordial sculpting of the Belt. None of them can explain in a single model all the observed properties; the real history of the Kuiper Belt probably requires a combination of some of the proposed mechanisms.
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the formation of the Kuiper Belt by the outward transport of bodies during neptune s migration
Nature, 2003Co-Authors: H F Levison, Alessandro MorbidelliAbstract:The ‘dynamically cold Kuiper Belt’ consists of objects on low-inclination orbits between ∼40 and ∼50 au from the Sun. It currently contains material totalling less than a tenth the mass of the Earth1,2, which is surprisingly low because, according to accretion models3,4, the objects would not have grown to their present size unless the cold Kuiper Belt originally contained tens of Earth masses of solids. Although several mechanisms have been proposed to produce the observed mass depletion, they all have significant limitations5. Here we show that the objects currently observed in the dynamically cold Kuiper Belt were most probably formed within ∼35 au and were subsequently pushed outward by Neptune's 1:2 mean motion resonance during its final phase of migration. Combining our mechanism with previous work6,7, we conclude that the entire Kuiper Belt formed closer to the Sun and was transported outward during the final stages of planet formation.
