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

This paper reviews recent results on the dynamics of multiple-planet extra-solar systems, including main sequence stars and the pulsar PSR B1257+12 and, comparatively, our own Solar System. Taking into account the degree of gravitational interaction of the planets, the known planetary systems may be separated into four main groups: (Ia) Planets in Mean-motion resonance (Ib) Low-eccentricity near-resonant pairs; (II) Non-resonant planets with a significant secular dynamics; and (III) Weakly interacting planet pairs. Different analytical and numerical tools can help to understand the structure of the phase space, to identify stability mechanisms and to categorize different types of motions in the cases of more significant dynamical interaction. The origin of resonant configurations is discussed in the light of the hypothesis of planetary migration.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 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 photographic observations of 51 Peg with the known planetary companion which has been discovered on the basis of radial velocities (Mayor and Quelos 1995), are being performed at Pulkovo since 1995 by means of 65 cm refractor. So far 46 plates with 170 individual positions have been obtained. The mean error of one exposure is $0.^{\prime\prime}031$ and the error of one plate is $0.^{\prime\prime}020$. The external error of one plate or the error of unit weight is $0.^{\prime\prime}033$, while the error of one yearly position equals to $0.^{\prime\prime}010$. The aim of our observations is to investigate whether this star has some satellites of low mass (stellar or substellar) with periods of rotation from some years to a decade, or more. At present we have the possibility to study its motion over a time span of 8 years and to learn of probable perturbations due to the presence of possible satellites with the periods 0.5–6.0 years and with masses more than $0.2M_\odot$. The absence of satellites with such periods and masses has been shown by means of our observations. The results are compared with the Pulkovo series of the star Gliese 623, whose satellite with the period of $3.76$ yr and mass of $0.09M_\odot$, has been confirmed by observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyze the secular interactions of two coplanar planets based on a high order (order 12) expansion of the perturbative potential in powers of the eccentricities. The model depends on only two parameters (the ratio of semi-major axis and the mass ratio of the planets) and can be reduced to a one degree of freedom system, allowing for an exhaustive parametric analysis. Following Pauwels (1984) we map the phase space on a sphere, avoiding in this way the artificial singularities introduced by other mappings. We show that the twelve order expansion is able to describe correctly most of the exosolar planetary systems discovered so far, even if the eccentricities of these planets are considerably larger than the eccentricities of our own solar system. The expansion is even able to reproduce, at moderate eccentricities, the secular resonances discovered numerically by Michtchenko and Malhotra (2004) at moderate to large eccentricities.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This paper explores the advantages of using gravity assisted trajectories to perform flyby and rendezvous missions to accessible near-Earth asteroids (NEAs), in terms of the total velocity budget required for the mission. Combining the Opik's formalism of close encounters with the Monte Carlo sampling technique and Lambert trajectories, we give a general picture of the accessibility regions for NEAs in phase space of orbital elements, without considering the phasing requirements between bodies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We show the utility of the Systematic Ranging technique by analyzing the orbit determination of asteroid 2004 FU$_{162}$, which passed approximately 6400 km from the surface of the Earth on March 31, 2004. The limited observations introduce strong nonlinearities that must be accounted for when estimating the actual encounter distance.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

Recent years have seen a revolution in the possibility to understand cometary capture, i.e., the origin of the cometary population that moves in orbits confined to the inner Solar System. This is due to the discovery of the major source populations: the Edgeworth-Kuiper belt, and the scattered disk. We review the current understanding of the links between the distant sources, including the Oort cloud, and the observed, short-period population, and the problems that remain. Some highlights of present research in this field will serve to illustrate recent progress and major issues that are currently arising.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

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

A complete study is made of the 5/2 resonant motion of two planets revolving around a star, in the model of the general planar three body problem. Families of 5/2 resonant symmetric periodic orbits are computed numerically, for the masses of the extrasolar system 47 UMa. The phase of the two planets (alignment or antialignment of perihelia and position of each planet at perihelion or aphelion) plays an important role, and the change of the phase, other things being the same, may destabilize the system. Stable motion exists even in the case where the two planetary orbits intersect. A small value of the eccentricities, for the same phase, stabilizes the system. The above results are applied to the study of 47 UMa, which according to some observations is close to the 5/2 resonance.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A novel method for the preliminary identification of asteroids at discovery and a few days thereafter is being developed in Helsinki. Having two different sets of asteroid observations, the goal is to identify all possible pairs of objects between the sets. An arbitrary asteroid can either remain unidentified, or be preliminary linked to one or more asteroids. In the case of ambiguity, the final decision must usually be based on additional observations. We use a multistep approach, during which possible pairs of objects are first selected by comparing ephemerides that have been generated for three common epochs. The method has been successfully tested using both Very Large Telescope observations, and simulated observations of near-Earth and main-belt objects. Identification results of simulated observations indicate that the observing strategy promoted by the Minor Planet Center might not be the best one, at least for the purposes of identification. The ultimate goal is to produce a real-time asteroid identification tool for ESA's astrometric space observatory Gaia, the Lowell Observatory Near-Earth-Object Search, the Near-Earth Space Surveillance mission, and the Nordic Near-Earth Object Network. The tool could also benefit large-scale surveys done with the Large Synoptic Survey Telescope, and the Discovery Channel Telescope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

To date, more than 130 extrasolar planets around main sequence stars are revealed mainly by the Doppler radial velocity measurements. Due to the observational biases, most of the detected planets are moving in orbits close to the host stars, with some in highly eccentric orbits. Dynamical processes during the late stage of planet formation are important to account for the present orbital properties. These processes include: planet migrations and resonance trappings caused by gravitational interactions between protostellar disk and planets, dynamical scattering due to interactions between planets, etc. In this paper, we review the major effects of these dynamical processes on the orbital characteristics of the planet systems.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

During the final production stages of the above article, the images of Figures 4 and 5 were transposed. The correct layout, with legends are reproduced below.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Results of the photographic observations of 61 Cyg are given. The orbital elements and mass ratio of the components of the pair are calculated. The preliminary orbit of a hypothetical satellite with a period of 6.5 yr is given.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

An internacional project “Lithium in magnetic Ap stars” has been run since 1996 with the purpose of creating an observational database allowing systematic studies of the abnormal occurence of lithium on the surface of cool Ap stars. The 2.6 m telescope at the Crimean Astrophysical Observatory, the ESO CAT, ESO 1.52 m telescope with FEROS, the Nordic Optical Telescope, and the 74″ telescope at Mount Stromlo were employed to collect observations at the regions of the lithium resonance lines $\lambda 6103$ and $\lambda 6708 \AA$.

Observations of the roAp-stars HD 83368, HD 60435 and HD 3980 revealed considerable periodical Doppler shifts of the line of lithium $\lambda 6708 \AA$ which can be explained by the presence of lithium spots on their surfaces. Conjunction with structures of the magnetic field is apparent.

A detailed study of the blend at $\lambda 6708 \AA$ in HD 101065 confirmed the anomalous overabundance of lithium amounting to 3.1 dex, as well as unusual isotopic ratio $^6{\rm Li}/^7 {\rm Li} \sim 0.3$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of observations made over three weeks using the UCT CCD Photometer on the 0.75-m telescope at the South African Astronomical Observatory. Candidate long period roAp stars were identified from their positions on the H-R diagram and observed for a typical period of 4 hr to test for the existence of pulsations, with particular emphasis on pulsations with periods in excess of 15 min. Although 13 stars were successfully observed, none exhibited significant pulsations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html