[en] A quantitative study of periodic orbits and particle trapping near them in the gravitational field of a uniformly rotating homogeneous solid parallelepiped is made. It is found that particle trapping leads to the possibility of formation of ring-like structures around the parallelepiped and blob-like concentrations around the equilibrium points of the parallelepiped. (Auth.)

[en] Assuming that the potential field on the plane of symmetry of a nearly axisymmetric galaxy is a polynomial of the fourth degree, we study the conditions of existence and stability of the main types of periodic orbits. We verify the theoretical results by numerical calculations. (author)

No abstract available

[en] When two stars are in orbit about each other, tidal forces cause an exchange of energy and angular momentum between the orbital motion and the fluid motion of each star about its own centre of mass. The orbit is progressively altered and one or both stars may be catastrophically disrupted. Two numerical methods are used to examine the motion: a 'normal-mode' analysis, based on linear perturbation analysis, and a 'smooth particle hydrodynamics' method which can follow arbitrary fluid motion in three dimensions

[en] Various properties of Keplerian orbits traced by satellites that are launched from one and the same spatial point with different initial velocities are discussed. Two families of elliptical orbits are investigated, namely the sets of orbits produced by a common direction but different magnitudes of the initial velocities, and by a common magnitude but various directions of the initial velocities. For the latter family, the envelope of all the orbits is found, which is the boundary of the spatial region occupied by the orbits

[en] Recent studies have attributed certain properties of the Earth's atmosphere to excess orbital angular momentum of impinging meteoroids. A realistic analysis of meteor observations does not support the existence of this excess. (Auth.)

[en] A first order analysis of current selenodetic and selenochronological data indicates that the present lunar figure was formed 3.0 +- 0.5 x 10⁹ years ago at an earth-moon distance of 20.4 +- 2.3 earth radii. This datum and data from a variety of sources are used to define the time evolution of the earth-moon distance. It is shown that there was a sudden increase in this distance about 2 x 10⁹ years ago when the Q of the earth must have decreased by a factor of 5. This change in Q correlates well with the onset of rapid continental growth and hence the expansion of shallow sea- and continental shelf waters as shown in the geological record for this time

[en] Although the circular photon orbit and ISCO for the Kerr black hole remain distinct from each other and from the horizon in the extremal spin limit on a constant Boyer-Lindquist time slice, on a horizon-crossing slice they both coincide with the null generators of the horizon. Communicated by E Poisson (note)

[en] Using a scintillation detector and an ionization chamber, radiation conditions along the Mir orbital complex trajectory are studied. It is shown that the time dependence of the measured dose in solar flare events is ambiguously related to the time dependence of the readings of an individual ground-based monitor, and the maximum dose in the orbit is ambiguously determined by the maximum in the neutron monitor counts

No abstract available