Citation
Pan, Margaret WheiJie (2006) Slices of theoretical astrophysics: planetary dynamics and relativistic explosions. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd05252006181025
Abstract
This thesis presents studies in two distinct areas of theoretical astrophysics: dynamics of planetary systems and relativistic fluid flows from shocks emerging from stellar envelopes. The first pertains to the early solar system, planet formation, and extrasolar planets; the second is related to extreme explosions like gammaray bursts and supernovae. We present two investigations of the dynamics and population evolution of small solar system bodies. First, we explore the dynamics of meanmotion resonances for a test particle moving in a highly eccentric longperiod orbit in the restricted circular planar threebody problem  a scenario relevant to the scattered Kuiper belt and the formation of the Oort cloud. We find an infinite number of analogues to the Lagrange points; a simple explanation for the presence and absence of asymmetric librations in particular meanmotion resonances; and a criterion for the onset of chaotic motion at large semimajor axes. Second, we study the size distribution of Kuiper belt objects (KBOs), which is observed to be a broken power law. We apply a simple mass conservation argument to the KBO collisional cascade to get the powerlaw slope for KBOs below the break; our result agrees well with observations if we assume KBOs are held together by selfgravity rather than material strength. We also explain the location and time evolution of the break in the size distribution. We also present investigations of the flow which results when a relativistic shock propagates through and then breaks out of a stellar envelope with a polytropic density profile. This work informs predictions of the speed of and energy carried by the relativistic ejecta in supernovae and perhaps in gammaray bursts. We find the asymptotic solution for the flow as the shock reaches the star's edge and find a new selfsimilar solution for flow of hot fluid after the shock breakout. Since the postbreakout flow acclerates by converting its thermal energy into bulk kinetic energy, the fluid in the flow eventually cools to nonrelativistic temperatures. We derive a second new selfsimilar solution which includes the cold portions of the flow. This second solution gives an exact relation between the terminal Lorentz factor of each fluid element and the Lorentz factor it acquired upon being shocked before breakout.
Item Type:  Thesis (Dissertation (Ph.D.)) 

Subject Keywords:  collisional cascades; planetary dynamics; relativistic shocks; similarity solutions 
Degree Grantor:  California Institute of Technology 
Division:  Physics, Mathematics and Astronomy 
Major Option:  Astrophysics 
Thesis Availability:  Public (worldwide access) 
Research Advisor(s): 

Group:  TAPIR 
Thesis Committee: 

Defense Date:  23 May 2006 
Record Number:  CaltechETD:etd05252006181025 
Persistent URL:  http://resolver.caltech.edu/CaltechETD:etd05252006181025 
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  2058 
Collection:  CaltechTHESIS 
Deposited By:  Imported from ETDdb 
Deposited On:  02 Jun 2006 
Last Modified:  18 Aug 2017 20:45 
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