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Numerical analysis of the Hills mechanism
Čížek, Kryštof ; Haas, Jaroslav (advisor) ; Brož, Miroslav (referee)
Interaction of three bodies is generally quite chaotic and a problem difficult to solve. Case in which binary star approaches third, heavier body is a special configuration of this problem and was investigated by J. G. Hills in his articles. In such interaction, either absolute breakup of the system to three independent bodies, survival of the binary star, or replacement of one component of the binary by the heavier body would occur - an exchange collision. If the replacement is to happen, the exchanged body is ejected away from the system with high velocity and such effect we call Hills mechanism. In such case the binary star usually has higher binding energy and is much more resistant if such situation were to occur again. However, Hills' results are not sufficient e.g. for effects within the core of our galaxy. Using numerical integration we modelled approximations of binary stars to a third, heavier body, thanks to which we could verify Hills' results and expand on them with initial conditions which are more suited to situations occuring within the core of our galaxy.
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Hydrodynamic and N-particle simulations of asteroid collisions
Ševeček, Pavel ; Brož, Miroslav (advisor) ; Wünsch, Richard (referee)
We study asteroidal breakups, i.e. fragmentations of targets, subsequent gravitational reaccumulation and formation of small asteroid families. We fo- cused on parent bodies with diameters Dpb = 10 km. Simulations were per- formed with a smoothed-particle hydrodynamics (SPH) code combined with an efficient N-body integrator. We assumed various projectile sizes, impact veloci- ties and angles (125 runs in total). Resulting size-frequency distributions are sig- nificantly different from results of scaled-down simulations with Dpb = 100 km targets (Durda et al. 2007). We thus derive new parametric relations describing fragment distributions, suitable for Monte-Carlo collisional models. We also characterize velocity fields and angular distributions of fragments, which can be used in N-body simulations of asteroid families. Finally, we discuss several uncertainties related to SPH simulations.
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Study of inclination change for the eclipsing binaries
Juryšek, Jakub ; Zasche, Petr (advisor) ; Brož, Miroslav (referee)
This thesis deals with the study of the eclipsing binaries with inclination changes, caused by orbital precession due to third body in the system. Methods of semiauthomatic detection of the inclination changing eclipsing binaries among huge lightcurves databases have been developed. These methods have been applied to the ASAS-3 and OGLE III LMC databases. As a result, 39 new systems suspected of orbital precession have been found and 33 of them are situated in the Large Magellanic Cloud, with only one previously studied system. Increasing the number of known multiple systems especially those located outside Milky Way allows to study inter-galactic differences in star formation. In this work, we bring detailed study of ten new systems and restrictions on the third body parameters are presented. Powered by TCPDF (www.tcpdf.org)
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Rotational dynamics of asteroids affected by thermal emission from topographic features
Ševeček, Pavel ; Brož, Miroslav (advisor) ; Henych, Tomáš (referee)
Infrared radiation emitted from an asteroid surface causes a torque that can significantly affect rotational state of the asteroid. The influence of small topographic features on this phenomenon, called the YORP effect, hasn't been studied yet in detail. In this work, we show that lateral heat diffusion in surface features of suitable sizes leads to the emergence of a local YORP effect which magnitude is comparable to the YORP effect due to the global shape. We solve a three- dimensional heat diffusion equation in a boulder and its surroundings by the finite element method using the FreeFem++ code. The contribution to the total torque is then inferred from the com- puted temperature distribution. We compare the torque for various boulder shapes and material properties. For an idealized boulder our result is consistent with an existing one-dimensional model. Topographic features may cause a spherical asteroid of radius 1 km on a circular orbit at 2.5 AU to undergo a rotational acceleration of about (2.2 ± 1.1) · 10−9 rad/day2 , which corresponds to the spin-up timescale of the order τ = (32 ± 16) Myr. We estimated a size distribution of boulders based on close-up images of (25143) Itokawa surface. Finally, we realized that topographic features of Itokawa can induce a rotational acceleration of the order 10−7...
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Interactions of migrating giant planets and small solar-system bodies
Chrenko, Ondřej ; Brož, Miroslav (advisor) ; Wünsch, Richard (referee)
Changes of semimajor axes of giant planets, which took place 4 billion years ago and evolved the Solar System towards its present state, affected various populations of minor Solar-System bodies. One of these populations was a group of dynamically stable asteroids in the 2:1 mean-motion resonance with Jupiter which reside in two islands of the phase space, denoted A and B, and exhibit lifetimes comparable to the age of the Solar System. The origin of stable asteroids has not been explained so far. Our main goal is to create a viable hypothesis of their origin. We update the resonant population and its physical properties on the basis of up-to-date observational data. Using an N-body model with seven giant planets and the Yarkovsky effect included, we demonstrate that the depletion of island A is faster compared to island B. We then investigate: (i) survivability of primordial resonant asteroids and (ii) capture of the population during planetary migration, using a recently described scenario with an escaping fifth giant planet and a jumping-Jupiter instability. We employ simulations with prescribed migration, smooth late migration and we statistically evaluate the results using dynamical maps. We also model collisions during the last 4 billion years. We conclude that the long-lived group was created by a...
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Asteroid families and their relation to planetary migration
Rozehnal, Jakub ; Brož, Miroslav (advisor) ; Vokrouhlický, David (referee)
In this thesis, we study how the planetary migration affects asteroid families. We identify the families among the Trojans of Jupiter by analysing their properties in the space of resonant elements, the size-frequency distribution and the colour indices. The previously reported number of families (10) seems to be overestimated, our analysis indicates that there is only one collisional family among Trojans with the parent-body size DPB > 100 km. We also performed a simulation of the long-term orbital evolution of the Trojan families. We used a modified version of the SWIFT symplectic integrator where the migration is set analytically. We found that the families are unstable even in the late stages of the migration, when Jupiter and Saturn recede from their mutual 1:2 resonance. Hence, the families observed today must have been created after the planetary migration ended. In the last part of the work, we study a formation of asteroid families in the Main Belt during the Late Heavy Bombardement. We simulate perturbations induced by migrating planets in the "jumping Jupiter" scenario (Morbidelli et al., 2010) and we conclude that big families (DPB > 200 km) created during the bombardement should be observable today.
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The application of the LSST in the physics of the small solar-system bodies
Sváda, Petr ; Brož, Miroslav (advisor) ; Wolf, Marek (referee)
This thesis is devoted to the description of the Large Synoptics Survey Telescope (LSST) and its use in the physics of small solar-system bodies. Based on the telescope optics parameters and the theory of signal and noise we calculate limiting magnitude of the LSST (24,9 0,4) mag (in the V band). This value, together with data from MPC and WISE databases, serve as an input parameter for the calculation of the minimum diameter ( ) m of a main-belt asteroid, that LSST will be able to observe. We also estimated that (160 ± 118) million asteroids could be observable by the LSST. Taking into account the planned observational strategy and cadence, we calculated that a sufficiently bright asteroid will be observed approximately 370 times. Finally, the possible applications of the LSST are discussed: e. g. a development of collisional models, explanation of orbital and rotational dynamics of sub-kilometer objects.
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Origin of asteroids in the 2:1 mean-motion resonance with Jupiter
Chrenko, Ondřej ; Brož, Miroslav (advisor) ; Hanuš, Josef (referee)
Asteroids located in the 2:1 mean-motion resonance with Jupiter are classified as stable (called Zhongguos), marginally stable (called Griquas) and unstable (called Zulus) according to their dynamical lifetime. The stable asteroids reside in two separate stable islands in the pseudo-proper element space. In this thesis, we update the resonant population on the basis of up-to-date observational data and we determine orbital and physical properties of the resonant population. Using collisional models, we demonstrate that the observed Zhongguos and Griquas might be up to 4 Gyr old, thus their origin might be related to the planetary migration. Performing dynamical N-body simulations, we test two hypotheses of the origin of the long-lived population: the primordial population scenario, and the asteroidal capture scenario. Our results imply that the resonant population is not primordial but it was rather formed by the asteroids captured from an asteroidal family located in outer main belt.
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Inner belt asteroids in the spin-orbital resonance
Vraštil, Jan ; Vokrouhlický, David (advisor) ; Brož, Miroslav (referee)
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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