Results 1 - 10 of 2024
Results 1 - 10 of 2024. Search took: 0.025 seconds
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[en] 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.
[en] We have analyzed the first 3.75 years of data from the Taiwanese American Occultation Survey (TAOS). TAOS monitors bright stars to search for occultations by Kuiper Belt objects (KBOs). This data set comprises 5 x 105 star hours of multi-telescope photometric data taken at 4 or 5 Hz. No events consistent with KBO occultations were found in this data set. We compute the number of events expected for the Kuiper Belt formation and evolution models of Pan and Sari, Kenyon and Bromley, Benavidez and Campo Bagatin, and Fraser. A comparison with the upper limits we derive from our data constrains the parameter space of these models. This is the first detailed comparison of models of the KBO size distribution with data from an occultation survey. Our results suggest that the KBO population is composed of objects with low internal strength and that planetary migration played a role in the shaping of the size distribution.
[en] In the recent years, the 'Nice' model of solar system formation has attained an unprecedented level of success in reproducing much of the observed orbital architecture of the solar system by evolving the planets to their current locations from a more compact configuration. Within the context of this model, the formation of the classical Kuiper Belt requires a phase during which the ice giants have a high eccentricity. An outstanding question of this model is the initial configuration from which the solar system started out. Recent work has shown that multi-resonant initial conditions can serve as good candidates, as they naturally prevent vigorous type-II migration. In this paper, we use analytical arguments, as well as self-consistent numerical N-body simulations to identify fully resonant initial conditions, whose dynamical evolution is characterized by an eccentric phase of the ice giants, as well as planetary scattering. We find a total of eight such initial conditions. Four of these primordial states are compatible with the canonical 'Nice' model, while the others imply slightly different evolutions. The results presented here should prove useful in further development of a comprehensive model for solar system formation.
[en] This chapter discusses some of the main effects of the interaction of planets with remnant planetesimal disks, after the disappearance of the gas. It focuses on planet migration and its possible outcomes. In particular, we discuss the possibility that the migration of the planets leads them into an unstable configuration which changes drastically the structure of the system. The late heavy bombardment (LHB) of the terrestrial planets, occurring 650 Myr after planet formation, is a strong indication that this kind of evolution occurred in our solar system. Other stars show evidence of intense comet showers, which may indicate that LHB-analogs are ongoing in those systems at the current time
[en] We have obtained a full suite of Spitzer observations to characterize the debris disk around HR 8799 and to explore how its properties are related to the recently discovered set of three massive planets orbiting the star. We distinguish three components to the debris system: (1) warm dust (T ∼ 150 K) orbiting within the innermost planet; (2) a broad zone of cold dust (T ∼ 45 K) with a sharp inner edge orbiting just outside the outermost planet and presumably sculpted by it; and (3) a dramatic halo of small grains originating in the cold dust component. The high level of dynamical activity implied by this halo may arise due to enhanced gravitational stirring by the massive planets. The relatively young age of HR 8799 places it in an important early stage of development and may provide some help in understanding the interaction of planets and planetary debris, an important process in the evolution of our own solar system.
[en] Estimates of the size distribution of Main Belt asteroids suggest that there is an undetected population of approximately 10 trillion objects in the meter-to kilometer-range. These small objects are highly diverse impact generated fragments of ancient asteroids. This vast and so far unexplored resource of small bodies holds a rich variety of information on the origin and evolution of our Solar System. Current Earth-based telescopes have, with a few exceptions, not been able to detect the faint and distant meter-sized asteroids in the Main Belt. Deep exposures cannot be used, unless the object can be tracked, which is not possible for an object in an unknown orbit. Small asteroids can be observed close up from a spacecraft but, so far, missions to the Main Belt have not had the ability to detect new small asteroids (with the exception of Dactyl, the kilometer-sized asteroid, that was found orbiting the much larger asteroid Ida). Due to the rapidly changing geometry, small asteroids can only be observed from a spacecraft for a very limited time, hence it is not possible to operate a spacecraft from the distant Earth and a fully autonomous mission is required. The technology required to build such spacecrafts does exist and has been tested in space. We have explored the scientific potential of deep space missions to detect and study small asteroids from spacecrafts traveling through the asteroid Main Belt
[en] The current concepts of the origin and evolution of the Solar System are discussed, and some notions about extrasolar planets are reviewed. The present status of and future prospects for space exploration in Russia and abroad are examined. (conferences and symposia)
[en] We perform numerical simulations to study the secular orbital evolution and dynamical structure of the quintuplet planetary system 55 Cancri with the self-consistent orbital solutions by Fischer and coworkers. In the simulations, we show that this system can be stable for at least 108 yr. In addition, we extensively investigate the planetary configuration of four outer companions with one terrestrial planet in the wide region of 0.790 AU ≤ a ≤ 5.900 AU to examine the existence of potential asteroid structure and Habitable Zones (HZs). We show that there are unstable regions for orbits about 4:1, 3:1 and 5:2 mean motion resonances (MMRs) of the outermost planet in the system, and several stable orbits can remain at 3:2 and 1:1 MMRs, which resembles the asteroid belt in the solar system. From a dynamical viewpoint, proper HZ candidates for the existence of more potential terrestrial planets reside in the wide area between 1.0 AU and 2.3 AU with relatively low eccentricities. (research paper)
[en] A major objective in solar system exploration has to be the insertion of appropriate biology-oriented experiments in future missions. We discuss various reasons for suggesting that this type of research be considered a high priority for feasibility studies and, subsequently, for technological development of appropriate melters and submersibles. With the assumption that Darwin's theory is valid for the evolution of life anywhere in the universe, various degrees of convergent phenomena argue in favor of the conjecture that universal evolution of intelligent behavior is just a matter of time and preservation of steady planetary conditions. A preliminary test of this conjecture is feasible with experiments involving evolutionary biosignatures on Europa. (author)
[en] Numerical simulations of accretion of planetary embryos from small planetesimals are described. In the terrestrial region, runaway growth proceeds as a wave propagating outward, producing an 'oligarchy' of embryos. The efficiency of accretion, i.e. the mass loss due to fragmentation, depends on the initial size of the planetesimals. In the outer region of the disk, the growth of embryos is not a localized process. At larger heliocentric distances, gravitational scattering and long-range perturbations become more significant, and tend to inhibit runaway growth