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Recent asteroid breakups and accretion of interplanetary dust on the Earth
Pokorný, Petr ; Vokrouhlický, David (advisor) ; Šolc, Martin (referee)
The major aim of the thesis is an analysis of an accretion of dust originating from breakup events of Emilkowalski and YC2 asterodial families. Using a numerical integrator we follow orbits of individual dust particles, some of which will result in an impact onto one of the planets in the Solar system. Employing some non-trivial transformation we compare recorded impacts onto the Earth to available dust measurements values acquired in antarctic ice-cores. We also analyse the dynamical e ffects of Poynting-Robertson e ffect and their influence on the dust particles of variable sizes.
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Rovnice vedení tepla ve fyzice planetek a meteoroidů
Pohl, Leoš ; Brož, Miroslav (advisor) ; Vokrouhlický, David (referee)
Non-gravitational forces caused by thermal emission of photons can significantly change orbits and spin states of asteroids in the long term. A solution of the Heat Conduction Equation (HCE) in an asteroid is necessary to evaluate the forces. Finite Difference Methods (FDMs) are implemented in a Fortran numerical HCE solver to calculate a temperature distribution within a system of 1-dimensional slabs which approximate the asteroid. We compare the methods w.r.t. convergence, accuracy and computational efficiency. The numerical results are compared with a simplified steady-state analytical solution. We calculate the non-gravitational accelerations and resulting semimajor axis drift from the numerical results. The implemented FDMs are shown to be convergent with denser grids and the best method has been selected. The analytical solution provides a good first-guess estimate of the temperature amplitude. The drift in semimajor axis of the tested asteroids, which is due to the non-gravitational forces, is in order-of-magnitude agreement with more accurate models and observational data.
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Inner belt asteroids in the spin-orbital resonance
Vraštil, Jan ; Vokrouhlický, David (advisor)
Context: Slivan (2002) determined spin state of ten asteroids in the Koronis family. Surprisingly, all four asteroids with prograde sense of rotation were shown to have spin axes nearly parallel in the inertial space. All asteroids with retrograde sense of rotation had large obliquities and rotation periods either short or long. It was shown that Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect can explain all these peculiar facts. In particular, it drives spin axes of the prograde rotators to be captured in a secular spin-orbital resonance known as Cassini state 2. Vokrouhlický et al. (2002) dubbed these configurations "Slivan states". Aims: A question arises whether Slivan states could exist also in other regions of the main asteroid belt, in particular its inner part, where observations are most easily obtained. Here, however, dynamical difficulties arise due to convergence of the proper frequency s and the planetary frequency s6. We investigate possibilities of a long-term stable capture in the Slivan state in the inner part of the main belt. Method: We used SWIFT integrator to determine orbital evolution of selected asteroids in the inner part of the main belt. In the case of 20 Massalia, we observed the asteroid in 2011, and used these new data to help better solve the rotation state using the...
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Short-lived Delocalization and Absorption by Light
Vokrouhlický, David ; Mančal, Tomáš (advisor) ; Veis, Libor (referee)
Coherent exciton delocalization improves the light harvesting function of photosyn- thetic antennae by creating conditions for very fast excitation transfer in space. This thesis focuses on two different effects creating coherence - short-lived excitation by light and weak coupling between pigments that is present in the system on longer timescales. The evolution and relaxation of simple systems - the dimer and trimer - are calculated. The core of this thesis are newly developed numerical methods for distinguishing and quantifying the effect of the two types of coherence throughout evolution, which are applied to the aforementioned systems. 1
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Yarkovsky and YORP Effects in Dynamics of Small Bodies of the Solar System
Žižka, Jindřich ; Vokrouhlický, David (advisor) ; Čapek, David (referee) ; Neslušan, Luboš (referee)
In this thesis, we study the influence of non-gravitational perturbations induced by the Yarkovsky/YORP effect and solar radiation pressure (SRP) on the orbital evolution of selected asteroids, asteroid families and pairs. These perturbations are of great importance if one wants to perform precise and long-term propagation of meter-sized and kilometer-sized bodies. Although they have found many applications in the Solar System, here, we particularly investigated how they influence the orbit of near-Earth asteroid (99942) Apophis and what is their role in the age determination of asteroid families and pairs. Our numerical simulations showed that the perturbations of Apophis' orbit caused by the SRP are orders of magnitude smaller than those produced by the Yarkovsky effect. The age determination of asteroid families and pairs was another pillar of this work. Over the past decade it turned out that the Yarkovsky effect must be taken into account for backward propagation of pair/family members. We modified the current method for estimating the age of asteroid pairs to be suitable for weakly convergent cases and discovered 7 young pairs with similar-sized components, which is in contradiction with the current theory of pair formation. In addition, we focused on an interesting pair of asteroids -...
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Inner belt asteroids in the spin-orbital resonance
Vraštil, Jan ; Vokrouhlický, David (advisor)
Context: Slivan (2002) determined spin state of ten asteroids in the Koronis family. Surprisingly, all four asteroids with prograde sense of rotation were shown to have spin axes nearly parallel in the inertial space. All asteroids with retrograde sense of rotation had large obliquities and rotation periods either short or long. It was shown that Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect can explain all these peculiar facts. In particular, it drives spin axes of the prograde rotators to be captured in a secular spin-orbital resonance known as Cassini state 2. Vokrouhlický et al. (2002) dubbed these configurations "Slivan states". Aims: A question arises whether Slivan states could exist also in other regions of the main asteroid belt, in particular its inner part, where observations are most easily obtained. Here, however, dynamical difficulties arise due to convergence of the proper frequency s and the planetary frequency s6. We investigate possibilities of a long-term stable capture in the Slivan state in the inner part of the main belt. Method: We used SWIFT integrator to determine orbital evolution of selected asteroids in the inner part of the main belt. In the case of 20 Massalia, we observed the asteroid in 2011, and used these new data to help better solve the rotation state using the...
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Dynamics of small bodies in the Solar System: from dust particles to asteroid
Pokorný, Petr ; Vokrouhlický, David (advisor) ; Borovička, Jiří (referee) ; Wiegert, Paul (referee)
In this thesis, we study two different topics: collisional probability between two bodies and dynamics of the sporadic meteoroids in the Solar System. Determination of the collision probabilities in the Solar System is one of the important problems in mod- ern celestial mechanics. Here, we generalize classical theories of the collisions between two bodies by Öpik, Wetherill or Greenberg by including the Kozai-Lidov oscillations, a mechanism that significantly change orbital eccentricity and inclination in the Solar System. Sporadic meteors have been studied for many decades providing a wealthy re- source of data. Here, we build dynamical steady-state models for all known populations observed in the sporadic meteoroid complex based on the latest and most precise data provided by Canadian Meteor Orbit Radar (CMOR). Our models using the latest theo- ries for cometary populations in the Solar System accurately describe observed sporadic background population. Our results are in agreement with observations provided by space probes IRAS and LDEF.
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