The source of long-period comets can be numerically modeled by means of Monte Carlo simulation of the Oort cloud dynamics. Tracing a comet motion under the galactic perturbations over a long time interval requires taking into account of planetary perturbations. A method for the approximate treating of the planetary perturbations in such simulations is described. Some peculiarities found in planetary action on long-period simulated cometary sample are also discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

2003 VB$_{12}$ (Sedna) is as much distinguished by its considerable size as by its extremely unusual orbit, which has perihelion at about $q=76$ AU with semi-major axis $a=533$ AU (Brown et al. 2004, JPL Horizons). Thus it is effectively decoupled from both Neptune and the Galactic tide (Fernandez 1997). Brown et al. (2004) and Morbidelli & Levison (2004) maintain that only scattering by a so-far-unobserved “Planet X” or by an errant star could produce such a high-perihelion orbit for a scattered-disk KBO. While a close encounter is plausible, given the Sun's likely birth in an open cluster, such an interaction would profoundly disturb the Oort cloud and would require fundamental revision to the present theories of its formation.

Although the planets cannot significantly affect VB$_{12}$'s orbit through close approaches, resonant perturbations could conceivably produce secular effects on it. To explore this possibility, we have numerically integrated test particles with $480 < a < 580$ AU and a fixed $q=76$ AU. Including the four giant planets, but ignoring the Kuiper Belt and the inner Oort Cloud, as well as the Galactic tide, we find multiple resonances, some of which perturb significantly the test particles' eccentricity more strongly than the leading secular terms. We identify these resonances as variants of the very high-order ($n_N > 60 \n$) mean-motion commensurabilities between Neptune and VB$_{12}$. Although unprecedented, these extremely high-order resonances can be significant due to VB$_{12}$'s very high eccentricity ($e=0.86$). Even powers of eccentricity beyond sixty are still on the order of $10^{-4}$, which is comparable to the strength of low-order resonances involving near-circular orbits. We extrapolate the possible long-term drift rate and estimate the likelihood of such resonances producing an “inner Oort cloud” population consistent with VB$_{12}$ over the age of the Solar System. Finally we discuss how planetary migration and the Kuiper-Belt's depletion might have affected VB$_{12}$'s putative resonance.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In the framework of the restricted three body problem, the resonant periodic orbits associated with the Kuiper belt dynamics are studied. Particularly, all the first, second and third order exterior mean motion resonances with Neptune located up to 50A.U. and the asymmetric resonances (beyond the 48 A.U.) are considered. We present the bifurcation points of families of periodic orbits of the planar circular problem from which families of periodic orbits are generated in the planar elliptic and in the 3D circular problem. Similarities and differences between the various resonant cases are noticed. The relation between the distribution of the bifurcation points and the population of small bodies at the particular resonances is discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The origin of stony meteorites landing on Earth today is directly linked to the history of the main belt, which evolved both through collisional evolution and dynamical evolution/depletion. In this paper, we focus our attention on the main belt dynamical evolution scenario discussed in Petit et al. (2001). According to Petit et al., during the planet formation epoch, the primordial main belt contained several Earth masses of material, enough to allow the asteroids to accrete on relatively short timescales.

After a few My, the accretion of planetary embryos in the main belt zone dynamically stirred the remaining planetesimals to high enough velocities to initiate fragmentation. After a short interval, perhaps as long as 10 My, the primordial main belt was dynamically depleted of $>99$% of its material via the combined perturbations of the planetary embryos and a newly-formed Jupiter. The small percentage of objects that survived in the main belt zone became the asteroid belt. It has been shown that the wavy-shaped size-frequency distribution of the main belt is a “fossil” left over from this violent period (Bottke et al. 2004).

Using a collisional/dynamical model of this scenario, we tracked the evolution of stony meteoroids produced by catastrophic disruption events over the last several Gy. We show that most stony meteoroids are a byproduct of a collisional cascade derived from large and ancient asteroid families or smaller, more recent breakup events. The meteoroids are then delivered to Earth by drifting in semimajor axis via Yarkovsky thermal drag forces until they reach a resonance powerful enough to place them on an Earth-crossing orbit.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Meteor streams that form as a result of cometary activity around perihelion consist of both structured and background components. The former are often referred to as trails. A trail is created at each perihelion passage as a result of the meteoroids' range of orbital periods. Trail locations can be precisely calculated by numerical integrations, allowing predictions of meteor outbursts and storms. The initial distribution of meteoroids, which relates to the meteor shower profile, depends on the meteoroid production rate and ejection velocity distribution as functions of heliocentric distance and on solar radiation pressure. The profile can gradually evolve owing to other radiative forces. This paper reviews such work on these aspects of shower predictions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Planetary systems are made up of objects with sizes ranging from gas giant planets down to asteroids and on to micron sized dust. Dust in the zodiacal cloud in the solar system originates in the break-up of asteroids and comets and then migrates in toward the Sun due to P-R drag. The dynamical evolution of the dust is also affected by the gravitational perturbations of the solar system's planets, and the consequence of those perturbations is evident in the asymmetric and clumpy structure of the zodiacal cloud. In the last couple of years features in the cloud have been identified with asteroid collisions which occurred just a few Myr ago implying that steady state models for the zodiacal cloud will have to be reconsidered. Many extrasolar systems also harbor massive dust belts and the structures of those dust belts have been linked to perturbations from unseen planets. This paper reviews the dominant physical processes affecting the evolution of dust grains and describes the techniques which have been developed to model their dynamics and identify the sources of dust structures in both the solar system and extrasolar systems.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The current version of the IAU Meteor Data Centre catalogue of photographic orbits comprising the orbital and geophysical data of 4581 meteors is applied for a more representative search of the mean orbits of bolide meteor streams among photographic meteors. We have made the search based on a computerized stream search procedure utilizing the Southworth-Hawkins D-criterion. The results are compared with the previous similar analysis made by Porubčan & Gavajdová (1994).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We integrated the orbital evolution of 30,000 Jupiter-family comets, 1300 resonant asteroids, and 7000 asteroidal, trans-Neptunian, and cometary dust particles. For initial orbital elements of bodies close to those of Comets 2P, 10P, 44P, and 113P, a few objects got Earth-crossing orbits with semi-major axes $a<2$ AU and moved in such orbits for more than 1 Myr (up to tens or even hundreds of Myrs). Three objects (from 2P and 10P runs) even got inner-Earth orbits (with aphelion distance $Q<0.983$ AU) and Aten orbits for Myrs. Our results show that the trans-Neptunian belt can provide a significant portion of near-Earth objects, or the number of trans-Neptunian objects migrating inside the solar system can be smaller than it was earlier considered, or most of 1-km former trans-Neptunian objects that had got near-Earth object orbits for millions of years disintegrated into mini-comets and dust during a smaller part of their dynamical lifetimes. The probability of a collision of an asteroidal or cometary particle during its lifetime with the Earth was maximum at diameter $d\sim 100\,\mu$m. At $d<10\,\mu$m such probability for trans-Neptunian particles was less than that for asteroidal particles by less than an order of magnitude, so the fraction of trans-Neptunian particles with such diameter near Earth can be considerable.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The new cutting edge technologies have opened the possibility of using digital spectrometers to probe the sky. With the sampling rate of $\sim$400 Msamples/s and the capability to digitally process data in real-time it is possible to get wideband spectra covering the frequencies in the range 0-200 MHz with the resolution of a few kHz. This presentation will show how such a spectrometer can be applied to the forward-scattering method of meteor detection.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

To correctly take into account the solar wind drag equations for secular variations in the meteoroid orbital semimajor axes and eccentricities were obtained. The equations are similar to those derived for the Poynting- Robertson radiation drag (Wyatt and Whipple 1950). An estimation for the Geminid meteoroid stream shows that the ratios of corpuscular to radiation drags are 0.4 – 0.7 for particles of size $> 10 \mu m$, i.e. the effect is much stronger than was assumed before.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Interstellar dust grains approaching the Sun are influenced mainly by solar gravity, solar electromagnetic radiation and Lorentz force due to the existence of interplanetary magnetic field. These interactions together with the effect of the solar wind on dust grain and the effect of solar cycle are taken into account when modelling behaviour of interstellar dust in the vicinity of the Sun. As a consequence, nonspherical dust grains can be captured and survive in the solar system – they can orbit the Sun in sufficiently large distances from the Sun not to be thermally destroyed. On the other hand, captured spherical dust grains are practically all destroyed. Detailed numerical simulations showed an interesting behaviour of a quantity of the dimension of length cubed divided by time squared. The quantity behaves practically as an invariant of motion: it is a constant during the process when surviving captured interstellar grain is orbiting the Sun. The constancy is fulfilled with an accuracy better than 1%.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Nonspherical dust grains orbiting the Sun are influenced by solar electromagnetic radiation. Interaction of electromagnetic radiation with nonspherical grains is complex and analogy with spherical grains may not be physically justified. As a consequence, equation of motion for nonspherical grain is more general than the equation of motion for spherical particle. Application of this more general interaction to possible trapping of the grain in resonances with planet Neptune is investigated. Approximation of the planar circular restricted three-body problem with action of solar electromagnetic radiation on nonspherical grain is used.

The orbital evolution of nonspherical dust grains of radius $\approx$ 2 micrometers is numerically calculated. Attention is payed to exterior resonances with the Neptune, and the numerical experiments are concentrated on their possible high capture efficiency. Physical difference between possibilities for resonant captures for spherical and nonspherical dust particles is pointed out.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

More than 300 000 artificial debris particles with diameter larger than 1 cm are orbiting the Earth. The space debris population is similar to the asteroid belt, since it is subject to a process of high-velocity mutual collisions that affects the long-term evolution of its size distribution. The near–Earth space can be divided in three major regions where orbital debris is of concern: Low Earth Orbits (LEOs), below about 2000 km, Geosynchronous Orbits (GEOs), at an altitude of about 36000 km and the Medium Earth Orbits (MEOs) in between. The issues are in principle the same in the three regions, nevertheless they require different approaches and solutions. The space debris are composed by several different populations according to their source and their orbital region. A description of the nature and dynamics of the different populations in the low, medium and high orbital regimes is given. The impact risk posed by these debris is then briefly outlined.

The long term evolution of the whole debris population can be studied with computer models allowing the simulation of all the known source and sinks mechanisms. One of these codes is described and the evolution of the debris environment, over the next 100 years, under different traffic scenarios is shown, pointing out the possible measures to mitigate the growth of the orbital debris population.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The problem of escape/capture is encountered in many problems of the celestial mechanics – the capture of the giants planets irregular satellites, comets capture by Jupiter, and also orbital transfer between two celestial bodies as Earth and Moon. To study these problems we introduce an approach which is based on the numerical integration of a grid of initial conditions. The two-body energy of the particle relative to a celestial body defines the escape/capture. The trajectories are integrated into the past from initial conditions with negative two-body energy. The energy change from negative to positive is considered as an escape. By reversing the time, this escape turns into a capture. Using this technique we can understand many characteristics of the problem, as the maximum capture time, stable regions where the particles cannot escape from, and others. The advantage of this kind of approach is that it can be used out of plane (that is, for any inclination), and with perturbations in the dynamics of the n-body problem.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The results of a numerical simulation of the tidal evolution of the Earth-Moon system during the Phanerozoic epoch (the last 600 million years) are given. In most of the researches devoted to the solution of the problem the authors simplified and parametrized very complicated tidal phenomena to a primitive integral hump on the Earth's surface. As distinct from these the numerical model of the ocean tides in its most complete form is the core of the present study: the problem is solved for a viscous liquid in a paleoocean with variable outlines and depth allocations stimulated by the drift of the lithospheric platforms; the global interaction between the ocean and earth tides and the fluctuations of the gravitational field of the planet caused by them are taken into account. The astronomical component of the model is simplified. It is assumed that the Earth-Moon system is isolated, the Moon's orbit circular and the moment of inertia of the Earth constant during the Phanerozoic epoch. It is shown that the evolution of the Earth-Moon system during the Phanerozoic was nonuniform and that the primary role in this process belongs to the geodynamic factor.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this study we give a first description of De Haerdtl's 3:7 inequality between the Jovian satellites Ganymede and Callisto and 1:5 inequality between the Saturnian Titan and Iapetus and the resonant arguments associated. For each inequality, 19 arguments are associated. The overlapping of resonant zones induces stochasic layers that the system might have crossed in the past thanks to tidal dissipation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In view of the possibility of employing Cassini's experiments for the diagnosis of the Saturnian ring system, local $N$-body simulations of low and moderately high optical depth regions of Saturn's main rings are presented. A special emphasis is made on fine-scale spiral structures (irregular cylindric wave-type structures of the order of 100 m or so) of Saturn's A, B, and C rings. It is predicted that Cassini spacecraft high-resolution images of Saturn's rings will reveal this kind of small-scale irregular density wave structure.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We approach the dynamics in proto-stellar systems via the two-body problem associated to an anisotropic Schwarzschild-type potential. On the basis of the natural symmetries of the characteristic vector field, and using variational methods (particularly the classical lower-semicontinuity method), we prove the existence of infinitely many families of symmetric periodic orbits.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this paper we present the new possibilities of classical ground – based observations for the purpose of improving the proper motions of some HIPPARCOS stars. The coordinates of asteroids, comets and other objects are calculated mostly by using the relative method and presented in a relevant reference frame via nearby stars (at the moment of observation) which materialize that reference frame. To improve the proper motions of stars we can use the latitude/universal time variations of ground – based data. Here, the results of improved proper motions in declination of some HIPPARCOS stars are presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We form a sample of nearby single stars. Their masses are estimated on the basis of the mass-luminosity relation. Our aim is to specify a reasonable space limit, i.e. a heliocentric volume, as small as possible, but to contain a sufficient number of stars so that an application of statistical laws becomes possible. Among the quantities calculated by us a special attention is paid to the mean mass of a single star and, also, to the local value of Agekyan's factor.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html