There is a complex inclination structure present in the transneptunian object (TNO) orbital distribution in the main classical belt region (between orbital semimajor axes of 39 and 48 au). The long-term gravitational effects of the giant planets make TNO orbits precess, but non-resonant objects maintain a nearly constant 'free' inclination ($I_\text{free}$) with respect to a local forced precession pole. Because of the likely cosmogonic importance of the distribution of this quantity, we tabulate free inclinations for all main-belt TNOs, each individually computed using barycentric orbital elements with respect to each object's local forcing pole. We show that the simplest method, based on the Laplace-Lagrange secular theory, is unable to give correct forcing poles for objects near the $ν_{18}$ secular resonance, resulting in poorly conserved $I_\text{free}$ values in much of the main belt. We thus instead implemented an averaged Hamiltonian to obtain the expected nodal precession for each TNO, yielding significantly more accurate free inclinations for non-resonant objects. For the vast majority (96\%) of classical belt TNOs, these $I_\text{free}$ values are conserved to $<1^\circ$ over 4 Gyr numerical simulations, demonstrating the advantage of using this well-conserved quantity in studies of the TNO population and its primordial inclination profile; our computed distributions only reinforce the idea of a very co-planar surviving 'cold' primordial population, overlain by a large $I$-width implanted 'hot' population.
The goal of this work is to determine the physical characteristics of resonant, detached and scattered disk objects in the transneptunian region, observed mainly in the framework of the "TNOs are Cool!" Herschel Open Time Key Program. Based on thermal emission measurements with the Herschel/PACS and Spitzer/MIPS instruments we determine size, albedo, and surface thermal properties for 23 objects using radiometric modelling techniques. This is the first analysis in which the physical properties of objects in the outer resonances are determined for a notable sample. In addition to the results fo…
Our understanding of the history of the solar system has undergone a revolution in recent years, owing to new theoretical insights into the origin of Pluto and the discovery of the Kuiper belt and its rich dynamical structure. The emerging picture of dramatic orbital migration of the planets driven by interaction with the primordial Kuiper belt is thought to have produced the final solar system architecture that we live in today. This paper gives a brief summary of this new view of our solar system's history, and reviews the astronomical evidence in the resonant populations of the Kuiper belt.
We analyze albedo data obtained using the Herschel Space Observatory that reveal the existence of two distinct types of surface among midsized transneptunian objects. A color-albedo diagram shows two large clusters of objects, one redder and higher albedo and another darker and more neutrally colored. Crucially, all objects in our sample located in dynamically stable orbits within the classical Kuiper belt region and beyond are confined to the bright-red group, implying a compositional link. Those objects are believed to have formed further from the Sun than the dark-neutral bodies. This color…
The surface composition of large Kuiper belt object 2007 OR10
我们提出的光度学和光谱的大型柯伊伯带对象2007 OR 10。这些数据显示了由于水冰而产生的显著的近红外吸收特征。虽然柯伊伯带中大多数吸收水冰的天体都具有水冰的光学中性颜色，但2007 OR 10是已知的最红的柯伊伯带天体之一。另一个大型柯伊伯带天体-夸欧尔-有类似的红色和水冰吸收，它的红色被假设是由于照射的少量甲烷能够保留在夸欧尔。2007 OR 10虽然比夸欧尔更温暖，但也有类似的挥发性保留，因为它足够大，其更强的重力仍然可以保留甲烷。因此，我们认为2007 OR 10上的红色也是由少量甲烷的保留引起的。阳性检测将需要2007年甲烷的光谱，或10将需要具有更高信噪比的光谱。柯伊伯带天体上的挥发物保留模型似乎继续在再现所有可用的观测结果方面做得很好。
The central objective of the New Horizons prime mission was to make the first exploration of Pluto and its system of moons. Following that, New Horizons has been approved for its first extended mission, which has the objectives of extensively studying the Kuiper Belt environment, observing numerous Kuiper Belt Objects (KBOs) and Centaurs in unique ways, and making the first close flyby of the KBO 486958 2014 MU69. This review summarizes the objectives and plans for this approved mission extension, and briefly looks forward to potential objectives for subsequent extended missions by New Horizon…
Extrasolar debris disks are the dust disks found around nearby main sequence stars arising from the break-up of asteroids and comets orbiting the stars. Far-IR surveys (e.g., with Herschel) showed that ~20% of stars host detectable dust levels. While dust temperatures suggest a location at 10s of au comparable with our Kuiper belt, orders of magnitude more dust is required implying a planetesimal population more comparable with the primordial Kuiper belt. High resolution imaging (e.g., with ALMA) has mapped the nearest and brightest disks, providing evidence for structures shaped by an underly…
The Classical Kuiper Belt is populated by a group of objects with low inclination orbits, reddish colors and usually belonging to a binary system. This so called Cold Classical Kuiper Belt is considered to have been formed in situ from primordial ice pebbles that coagulated into planetesimals hundreds of kilometers in diameter. According to this scenario, the accretion of pebbles into large planetesimals would have occurred through the streaming instability mechanism that would be effective in the primordial Solar System disk of gas and solids. Nevertheless other objects with the same color ch…
Dynamical mass estimates for the main asteroid belt and the trans-Neptunian Kuiper belt have been found from their gravitational influence on the motion of planets. Discrete rotating models consisting of moving material points have been used to model the total attraction from small or as yet undetected bodies of the belts. The masses of the model belts have been included in the set of parameters being refined and determined and have been obtained by processing more than 800 thousand modern positional observations of planets and spacecraft. We have processed the observations and determined the …
The origin of the orbital structure of the cold component of the Kuiper belt is still a hot subject of investigation. Several features of the solar system suggest that the giant planets underwent a phase of global dynamical instability, but the actual dynamical evolution of the planets during the instability is still debated. To explain the structure of the cold Kuiper belt, Nesvorny (2015, AJ 150,68) argued for a soft instability, during which Neptune never achieved a very eccentric orbit. Here we investigate the possibility of a more violent instability, from an initially more compact fully …
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 the…
The hypothesis that a massive Planet Nine exists in the outer solar system on a distant eccentric orbit was inspired by observations showing that the objects with the most distant eccentric orbits in the Kuiper belt have orbits which are physically aligned, that is, they are clustered in longitude of perihelion and have similar orbital planes. Questions have remained, however, about the effects of observational bias on these observations, particularly on the longitudes of perihelion. Specifically, distant eccentric Kuiper belt objects tend to be faint and only observable near their perihelia, …
The density of mid-sized Kuiper belt object 2002 UX25 and the formation of the dwarf planets
柯伊伯带中最大的天体（测得的密度为~1.5 g cm-3或更高）是由测得的密度低于1 g cm-3的小天体凝聚而成的，如果不援引最小天体中的显著孔隙度，就很难解释。如果确实出现这种孔隙，则测量的密度应在不再支持显著孔隙的尺寸处开始增加。在小行星中，这种转变发生在直径大于~350公里的情况下。在柯伊伯带中，在~350 km和~850 km之间没有进行过密度测量，这是孔隙度可能首先开始下降的直径范围。在这个范围内的物体可以提供小型柯伊伯带物体的岩石部分的关键测试。在这里，我们报告的轨道特性，质量和密度测定的2002年UX 25系统在柯伊伯带。对于这个直径约为650公里的天体，我们发现其密度为0.82+/-0.11 g cm-3，使其成为太阳系中已知密度低于纯水冰的最大固体天体。我们认为，该对象的孔隙度不太可能高于~ 20%，这表明岩石分数低。如果目前测量的柯伊伯带天体的密度是样本整体的合理代表，那么很难通过岩石成分与2002年UX 25推断的岩石成分一样低的小天体的凝聚来创建岩石质量成分为70%或更高的~1000 km和更大的柯伊伯带天体。
The non-resonant Kuiper belt objects (KBOs) between the 3:2 and 2:1 Neptunian mean motion resonances can be largely divided between a cold classical belt (CCB) and a hot classical belt (HCB). A notable difference between these two subpopulations is the prevalence of widely spaced, equal-mass binaries in the CCB and a much smaller but non-zero number in the HCB. The primary reason for this difference in binary rate remains unclear. Here using N-body simulations we examine whether close encounters with the giant planets during an early outer solar system instability may have disrupted primordial…
The Kuiper belt includes tens of thousands of large bodies and millions of smaller objects. The main part of the belt objects is located in the annular zone between 39.4 au and 47.8 au from the Sun, the boundaries correspond to the average distances for orbital resonances 3:2 and 2:1 with the motion of Neptune. One-dimensional, two-dimensional, and discrete rings to model the total gravitational attraction of numerous belt objects are considered. The discrete rotating model most correctly reflects the real interaction of bodies in the Solar system. The masses of the model rings were determined…
The four longest period Kuiper belt objects have orbital periods close to integer ratios with each other. A hypothetical planet with orbital period $\sim$17,117 years, semimajor axis $\sim$665 AU, would have N/1 and N/2 period ratios with these four objects. The orbital geometries and dynamics of resonant orbits constrain the orbital plane, the orbital eccentricity and the mass of such a planet, as well as its current location in its orbital path.
The outer solar system exhibits an anomalous pattern of orbital clustering, characterized by an approximate alignment of the apsidal lines and angular momentum vectors of distant, long-term stable Kuiper belt objects. One explanation for this dynamical confinement is the existence of a yet-undetected planetary-mass object, "Planet Nine (P9)". Previous work has shown that trans-Neptunian objects, which originate within the scattered disk population of the Kuiper belt, can be corralled into orbital alignment by Planet Nine's gravity over ~Gyr timescales, and characteristic P9 parameters have bee…
This paper shows that the inclinations of bodies captured into mean motion resonances in the Kuiper belt have remained very nearly unchanged, being only slightly increased from initial lower values by migration and/or by long-term planetary perturbations. Thus the observed maximum as high as ~ 30 deg of the i's of bodies in resonance must reflect either a broad initial range at least to that level for capturable bodies or an elevating process possibly exemplified by the sweeping of secular resonances. We have obtained capture probabilities for 2 well-populated resonances, showing reduced but f…
A distant, massive planet in the outer solar system has recently been proposed to explain some observed features of extreme trans-Neptunian objects (TNOs). Here we use N-body simulations of the formation of the Kuiper belt and Oort cloud as well as a survey simulator to compare models of the solar system with and without a 9th planet to one another as well as to observations. The main mechanism for TNOs to be deposited into the distant ($a$ > au), detached ($q$ > au) region of the Kuiper Belt in the 8-planet model is Kozai-Lidov oscillation of objects in mean motion resonances (MMR) with Neptu…
Much of the dynamical structure of the Kuiper belt can be explained if Neptune migrated over several AU, and/or if Neptune was scattered to an eccentric orbit during planetary instability. An outstanding problem with the existing formation models is that the distribution of orbital inclinations they predicted is narrower than the one inferred from observations. Here we perform numerical simulations of Kuiper belt formation starting from an initial state with Neptune at 20 < a_{N,0} < 30 AU and a dynamically cold outer disk extending from beyond a_{N,0} to 30 AU. Neptune's orbit is migrated int…
Centaurs are objects whose orbits are found between those of the giant planets. They are supposed to originate mainly from the TransNeptunian objects, and they are among the sources of NearEarth Objects.TransNeptunian Objects (TNOs) cross Neptune's orbit and produce the Centaurs. We investigate their interactions with main belt asteroids to determine if chaotic scattering caused by close encounters and impacts by these bodies may have played a role in the dynamical evolution of the main belt. We find that Centaurs and TNOs that reach the inner Solar System can modify the orbits of main belt as…
The cold classical Kuiper belt objects have low inclinations and eccentricities and are the only Kuiper belt population suspected to have formed in situ. Compared with the dynamically excited populations, which exhibit a broad range of colours and a low binary fraction of ~10% cold classical Kuiper belt objects typically have red optical colours with ~30% of the population found in binary pairs; the origin of these differences remains unclear. We report the detection of a population of blue-coloured, tenuously bound binaries residing among the cold classical Kuiper belt objects. Here we show t…
Models of the Solar System's dynamical evolution predict the dispersal of primitive planetesimals from their formative regions amongst 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 s…
This chapter reviews accretion models for Kuiper belt objects (KBOs), discussing in particular the compatibility of the observed properties of the KBO population with the streaming instability paradigm. Then it discusses how the dynamical structure of the KBO population, including the formation of its 5 sub-components (cold, hot, resonant, scattered and fossilized), can be quantitatively understood in the framewok of the giant planet instability. We also establish the connections between the KBO population and the Trojans of Jupiter and Neptune, the irregular satellites of all giant planets, t…
Origin of the peculiar eccentricity distribution of the inner cold Kuiper belt
Dawson and Murray-Clay（2012）指出，柯伊伯带内冷星群的内部（半长轴a<43.5天文单位），其轨道偏心率远小于稳定性限制的极限。在这里，我们确认他们的结果，在适当的元素空间中的轨道分布和稳定性。我们发现，所观察到的分布可能已经产生的缓慢扫描的4/7平均运动共振与海王星，伴随着海王星的迁移过程结束。热柯伊伯带的轨道分布在这一过程中没有受到明显的影响，原因在正文中讨论。因此，内部冷星群的特殊偏心率分布不能被明确地解释为冷星群在原地形成的证据，并且只有适度的偏心率激发;它可以简单地是海王星径向运动的标志，从适度偏心的轨道开始。我们讨论了这是如何同意的情况下，巨大的行星演化的动力学不稳定性，并可能与冷人口的径向运输。
Dynamically excited objects within the Kuiper belt show a bimodal distribution in their surface colors, and these differing surface colors may be a tracer of where these objects formed. In this work we explore radial color distributions in the primordial planetesimal disk and implications for the positions of ice line/color transitions within the Kuiper belt's progenitor populations. We combine a full dynamical model of the Kuiper belt's evolution due to Neptune's migration with precise surface colors measured by the Colours of the Outer Solar System Origins Survey in order to examine the true…
The K2 mission of the Kepler Space Telescope allowed the observations of light curves of small solar system bodies throughout the whole Solar system. In this paper we present the results of a collection of K2 transneptunian object observations, between Campaigns C03 (November 2014 -- February 2015) to C19 (August -- September, 2018), which includes 66 targets. Due to the faintness of our targets the detectability rate of a light curve period is $\sim$56%, notably lower than in the case of other small body populations, like Hildas or Jovian trojans. We managed to obtain light curve periods with…
The flyby of Pluto and Charon by the New Horizons spacecraft provided high-resolution images of cratered surfaces embedded in the Kuiper belt, an extensive region of bodies orbiting beyond Neptune. Impact craters on Pluto and Charon were formed by collisions with other Kuiper belt objects (KBOs) with diameters from ~40 kilometers to ~300 meters, smaller than most KBOs observed directly by telescopes. We find a relative paucity of small craters less than approximately 13 kilometers in diameter, which cannot be explained solely by geological resurfacing. This implies a deficit of small KBOs (les…
We analyze a detailed Nice model simulation of Kuiper Belt emplacement from Brasser & Morbidelli (2013), where Neptune undergoes a high eccentricity phase and migrates outward. In this work, which follows from Pike et al. (2017), we specifically focus on the details of structures within Neptune's mean motion resonances and in the high pericenter population of simulated trans-Neptunian Objects (TNOs). We find several characteristics of these populations which should be observable in the distant Solar System in future large-scale TNO surveys as a diagnostic of whether or not this mode of Neptune…
Within the dynamically cold low inclination portion of the Classical Kuiper Belt, there exists a population of weakly bound binary systems with a number of unusual properties; most notable of which is their extremely wide orbital separations; beyond 7% of their Hill radii. The stability and evolution of these Ultra-Wide Trans-Neptunian Binaries (TNBs) have, in the past, been studied extensively under the assumption that the primary evolving mechanisms are interactions between the binary components and impacting Trans-Neptunian Objects (TNOs). Here, we instead study their evolution as driven by…
The Kuiper belt is a population of icy bodies beyond the orbit of Neptune. A particularly puzzling and up-to-now unexplained feature of the Kuiper belt is the so-called `kernel', a concentration of orbits with semimajor axes a~44 AU, eccentricities e~0.05, and inclinations i<5 deg. Here we show that the Kuiper belt kernel can be explained if Neptune's otherwise smooth migration was interrupted by a discontinuous change of Neptune's semimajor axis when Neptune reached ~28 AU. Before the discontinuity happened, planetesimals located at ~40 AU were swept into Neptune's 2:1 resonance, and were car…
The Hubble Space Telescope (HST) measured the colors of eight Kuiper Belt Objects (KBOs) that will be observed by the New Horizons spacecraft including its 2019 close fly-by target the Cold Classical KBO (486958) 2014 MU69. We find that the photometric colors of all eight objects are red, typical of the Cold Classical dynamical population within which most reside. Because 2014 MU69 has a similar color to that of other KBOs in the Cold Classical region of the Kuiper Belt, it may be possible to use the upcoming high-resolution New Horizons observations of 2014 MU69 to draw conclusions about the …
Preliminary spacecraft trajectories for 45 Kuiper Belt Objects (KBOs) and Pluto suitable for launch between 2025 and 2040 are presented. These 46 objects comprise all objects with H magnitude < 4.0 or which have received a name from the International Astronomical Union as of May 2018. Using a custom Lambert solver, trajectories are modeled after the New Horizons mission to Pluto-Charon, which consisted of a fast launch with a Jupiter gravity assist. In addition to searching for Earth-Jupiter-KBO trajectories, Earth-Saturn-KBO trajectories are examined, with the option to add on a flyby to eith…
The centerpiece objective of the NASA New Horizons first Kuiper Extended Mission (KEM-1) was the close flyby of the Kuiper Belt Object KBO) 2014 MU69, nicknamed Ultima Thule. On 1 Jan 2019 this flyby culminated, making the first close observations of a small KBO. Initial post flyby trajectory reconstruction indicated the spacecraft approached to within ~3500 km of MU69 at 5:33:19 UT. Here we summarize the earliest results obtained from that successful flyby. At the time of this submission, only 4 days of data down-link from the flyby were available; well over an order of magnitude more data wi…
