Evolution of planetesimal velocities

Abstract A self-consistent set of equations for the velocity evolution of a general planetesimal population is presented. The equations are given in a form convenient for calculations of the early stages of planetary accumulation, when it is necessary to model the planetesimal swarm by the methods of gas dynamics, rather than follow the orbital evolution of individual bodies. To illustrate the relative importance of the various terms of these equations, steady-state velocities of a simple planetesimal population, consisting of two different sizes of bodies, are calculated. Dynamical friction is found to be an important mechanism for transferring kinetic energy from the larger planetesimals to the smaller ones, providing an energy source for the small planetesimals that is comparable to that provided by the viscous stirring process. When small planetesimals are relatively abundant, gas drag and inelastic collisions among the smaller bodies are of comparable importance for dissipating energy from the population.

[1]  G. Wetherill,et al.  Occurrence of Giant Impacts During the Growth of the Terrestrial Planets , 1985, Science.

[2]  George W. Wetherill,et al.  Accumulation of a swarm of small planetesimals , 1989 .

[3]  W. Saslaw,et al.  Gravitational Physics of Stellar and Galactic Systems: Finite spherical systems – clusters of galaxies, galactic nuclei, globular clusters , 1985 .

[4]  P. Barge,et al.  Thermal velocity equilibrium in the protoplanetary cloud , 1985 .

[5]  W. M. Kaula,et al.  A gravitational kinetic theory for planetesimals , 1980 .

[6]  C. Hayashi,et al.  The Gas Drag Effect on the Elliptic Motion of a Solid Body in the Primordial Solar Nebula , 1976 .

[7]  G. Wetherill,et al.  The range of validity of the two-body approximation in models of terrestrial planet accumulation: I. Gravitational perturbations , 1984 .

[8]  W. M. Kaula.  Equilibrium velocities of a planetesimal population , 1979 .

[9]  William K. Hartmann,et al.  Planetesimals to planets: Numerical simulation of collisional evolution , 1978 .

[10]  Richard J. Greenberg,et al.  From icy planetesimals to outer planets and comets , 1984 .

[11]  C. Lacey.  The influence of massive gas clouds on stellar velocity dispersions in galactic discs , 1984 .

[12]  George W. Wetherill,et al.  Accumulation of Mercury from planetesimals , 1988 .

[13]  S. Aarseth,et al.  A numerical simulation of the formation of the terrestrial planets , 1986 .

[14]  George W. Wetherill,et al.  The range of validity of the two-body approximation in models of terrestrial planet accumulation: II. Gravitational cross sections and runaway accretion , 1985 .

[15]  F. Shu,et al.  The collisional dynamics of particulate disks , 1985 .

[16]  JOHN S. Lewis,et al.  Numerical simulation of the final stages of terrestrial planet formation. , 1980 .

[17]  G. P. Horedt,et al.  Late stages of planetary accretion , 1985 .

[18]  A. Cazenave,et al.  Gaseous drag and planetary formation by accretion , 1985 .

[19]  Y. Nakagawa.  Statistical Behavior of Planetesimals in the Primitive Solar System , 1978 .

[20]  A. Harris.  Dynamics of planetesimal formation and planetary accretion , 1978 .

[21]  G. Wetherill.  Formation of the Terrestrial Planets , 1980 .

[22]  C. Hayashi,et al.  Accumulation of planetesimals in the solar nebula , 1983 .

[23]  Peter Goldreich,et al.  The Dynamics of Planetary Rings , 1982 .

[24]  A. Cazenave,et al.  Numerical experiment applicable to the latest stage of planet growth , 1982 .

[25]  G. Wetherill.  Accumulation of the terrestrial planets and implications concerning lunar origin , 1986 .