Planetary Sciences American and Soviet Research/Proceedings from the U.S.-U.S.S.R. Workshop on Planetary Sciences (1991) / Chapter Skim
Currently Skimming:
19. The Chaotic Dynamics of Comets and the Problems of the Oort Cloud
19. The Chaotic Dynamics of Comets and the Problems of the Oort Cloud
Pages 259-269
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 259... ...
The transport of comets differs greatly from the customary law of diffusion and noticeably decelerates the average comet flow. The vertical tidal effect of the galaxy in this region of motion is adiabatic and cannot noticeably alter cometary distribution.
|
From page 260... ...
If it was not a question of new comets, this equality would be a sufficiently obvious consequence of the impact of random collisions of stars with comets with highly eccentric orbits. However, numerical simulation, where the initial angular momentum value of the cometary protocloud is taken into account, also reveals the considerable impact it exerts on the size of the final Oort cloud and on the number of comets in it (Lopatnikov et al.
|
From page 261... ...
We will discuss below the conditions in which the dynamics of comets with long-period orbits become stochastic, the role of such comets in the overall model of the Oort cloud, and the influence of the galactic tidal forces on cometary dynamics. THE DYNAMIC CHAOS OF COMETS We can generate a straightforward idea of this chaos by looking at how a ball falls on a heavy plate in a gravity field (Figure 1, Zaslavskiy 1985)
|
From page 262... ...
Its mean energy at the moment of impact behaves asymptotically, as in ~ t2/3. The time for the ball to return back to the plate, naturally, increases. |
From page 263... ...
Let, for example, In denote the moment in time when the comet passes through its aphelion, Mn be the orbital momentum during passage through aphelion, and In denote the value of the Jovian phase during cometary passage through perihelion (preceding the time to)
|
From page 264... ...
(8) Since the perihelion changes little as a result of the collision (AM << M)
|
From page 265... ...
of a comet. The orbit points are plotted at the moment in time when a comet passes through the aphelion point.
|
From page 266... ...
The customary route is that collisions with stars operate in the zone of aphelion of a comet's orbit. Those comets in the loss cone region enter the visible zone, originally having a ~ 104 AU.
|
From page 267... ...
However, it is clear that the effect of tidal forces in the region of a significant portion of cometary orbits is adiabatic. Therefore, the tidal forces cannot substantially alter cometary distribution in the region < 104 AU.
|
From page 268... ...
The process of diffusive cometary transport differs from the usual process of diffusion and retards the characteristic time scale for the flux of comets toward the semi-major axes a. The action of the tidal forces does not alter this time scale significantly and is adiabatic (with the exception of the regions near the belt of the large planets and near the inner boundary of the Oort cloud)
|
From page 269... ...
1989. Space Research Institute, Moscow, in press Oort, J.H.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.