The origin and rotation of binary asteroids

Binary asteroids were detected in a variety of dynamical populations, including Near-Earth Asteroids (NEAs), the main belt (MB), Trojans, and transneptunian objects (TNO). We discuss a new “multi-impact” model for origin of all classes of binary objects, including binary asteroids, Pluto–Charon, and the Earth–Moon systems. Basic elements of the model is the effective accumulation of multi-impact meteoritic ejecta in satellite orbits due to the collisional interaction between impact debris and initial low-massive ring around the primary body. The origin of satellites of all small planets in the Solar System is a result of numerous meteoritic impacts on a rotated small planet and accumulation of meteoritic ejecta around the primary body. An important prediction from the new model is that asteroids with satellites rotate faster than single asteroids. The model is confirmed by comparisons of spin rates of binary asteroids and single objects. Average spin rate for main-belt asteroid is 2.45 ± 0.05 rev/d (single objects) and 4.51 ± 0.21 rev/d (13 binary objects); direction of rotation of satellites is prograde only (three samples). Average spin rate for NEAs is 2.72 ± 0.26 rev/d (single objects) and 9.28 ± 0.25 rev/d (19 binary objects)

Signatures of exosolar planets in dust debris disks

We apply our recently elaborated, powerful numerical approach to the high-resolution modeling of the structure and emission of circumstellar dust disks, incorporating all relevant physical processes. Specifically, we examine the resonant structure of a dusty disk induced by the presence of one planet. It is shown that the planet, via resonances and gravitational scattering, produces (1) an asymmetric resonant dust belt with one or more clumps intermittent with one or a few off-center cavities; and (2) a central cavity void of dust. These features can serve as indicators of a planet embedded in the circumstellar dust disk and, moreover, can be used to determine its major orbital parameters and even the mass of the planet. The results of our study reveal a remarkable similarity with various types of highly asymmetric circumstellar disks observed with the James Clerk Maxwell Telescope around Epsilon Eridani and Vega. The proposed interpretation of the clumps in those disks as being resonant patterns is testable -- it predicts the asymmetric design around the star to revolve, viz., by 1.2--1.6 deg/yr about Vega and 0.6--0.8 deg/yr about Epsilon Eri.Comment: to be published in ApJ Letters (v. 537, July 10, 2000), 5 pages, incl. 2 figures. Position of (color) Fig. 2 corrected to make the Figure caption fully readabl

Four Cometary Belts Associated with the Orbits of Giant Planets: A New View of the Outer Solar System's Structure Emerges from Numerical Simulations

Using numerical simulations, we examine the structure of a cometary population near a massive planet, such as a giant planet of the Solar system, starting with one-planet approximation (the Sun plus one planet). By studying the distributions of comets in semimajor axis, eccentricity, pericenter, and apocenter distances, we have revealed several interesting features in these distributions. The most remarkable ones include (i) spatial accumulation of comets near the planetary orbit (which we call the `cometary belt') and (ii) avoidance of resonant orbits by comets. Then we abandon one-planet approximation and examine as to how a cometary belt is modified when the influence of all four giant planets is taken into consideration. To this end, we simulate a stationary distribution of comets, which results from the gravitational scattering of the Kuiper belt objects on the four giant planets and accounts for the effects of mean motion resonances. Accounting for the influence of four giant planets makes the cometary belts overlapping, but nevertheless keeping almost all their basic features found in one-planet approximation. In particular, the belts maintain the gaps in the (a,e)- and (a,i)-space similar to the Kirkwood gaps in the main asteroid belt. We conclude that the large-scale structure of the Solar system is featured by the four cometary belts expected to contain 20-30 millions of scattered comets, and only a tiny fraction of them is currently visible as Jupiter-, Saturn-, etc. family comets.Comment: 16 pages, 1 table, 13 figures in the .ps.gz format, LaTEX uses aasms4. Accepted for publication in Planetary and Space Scienc

Dynamics of Gaseous Disks in a Non-axisymmetric Dark Halo

The dynamics of a galactic disk in a non-axisymmetric (triaxial) dark halo is studied in detail using high-resolution, numerical, hydrodynamical models. A long-lived, two-armed spiral pattern is generated for a wide range of parameters. The spiral structure is global, and the number of turns can be two or three, depending on the model parameters. The morphology and kinematics of the spiral pattern are studied as functions of the halo and disk parameters. The spiral structure rotates slowly, and its angular velocity varies quasi-periodically. Models with differing relative halo masses, halo semi-axis ratios, distributions of matter in the disk, Mach numbers in the gaseous component, and angular rotational velocities of their halos are considered.Comment: 22 pages, 11 figure