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Interactions of migrating giant planets and small solar-system bodies
Chrenko, Ondřej ; Brož, Miroslav (advisor)
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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Orbital and internal dynamics of terrestrial planets
Walterová, Michaela ; Běhounková, Marie (advisor) ; Efroimsky, Michael (referee) ; Brož, Miroslav (referee)
Title: Orbital and internal dynamics of terrestrial planets Author: Michaela Walterová Department: Department of Geophysics Supervisor: RNDr. Marie Běhounková, Ph.D., Department of Geophysics Abstract: Close-in exoplanets are subjected to intense tidal interaction with the host star and their secular evolution is strongly affected by the resulting tidal dissipation. The tidal dissipation not only provides an additional heat source for the planet's internal dynamics but it also contributes to the evolution of the planet's spin rate and orbital elements. At the same time, the tidal dissipation itself is also determined by the planet's thermal state and by the spin-orbital parameters. The evolutions of the orbit and of the interior are, therefore, intrinsically linked. In this work, we combine analytical and numerical techniques to gain insight into the interconnection between the internal properties and the orbital evolution, with special focus on the role of tides. After a general study of parametric dependencies of the tidal heating and tidal locking, we present a semi-analytical model assessing the coupled tidally-induced thermal-orbital evolution in systems consisting of a host star and one or two planets. Specifically, we study the thermal-orbital evolution in three systems inspired by existing low-mass...
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Early phases of formation and evolution of planetary systems
Chrenko, Ondřej ; Brož, Miroslav (advisor) ; Kley, Wilhelm (referee) ; Morbidelli, Alessandro (referee)
We study orbital evolution of multiple Earth-mass protoplanets in their natal protoplanetary disk. Our aim is to explore the interplay between migration of protoplanets driven by the disk gravity, their growth by pebble accretion, and accretion heating which affects gas in their neighbourhood. Radiation hydrodynamic (RHD) simulations in 2D and 3D are used to model the problem. We find that the heating torque, i.e. the torque exerted by asymmetric hot underdense gas near accreting protoplanets, significantly changes the migration. Specifically, it excites orbital eccentricities of migrating protoplanets, thus preventing their capture in chains of mean-motion resonances. The protoplanets then undergo numerous close encounters and form giant planet cores by mutual collisions. Additionally, if inclinations also become excited, we describe a new mechanism that can form binary planets by means of consecutive two-body and three-body encounters, with the assistance of the disk gravity. Finally, our 3D RHD simulations reveal a complex distortion of the gas flow near an accreting protoplanet, driven by baroclinic perturbations and convection. For specific temperature-dependent opacities of the disk, an instability is triggered which redistributes gas around the protoplanet and leads to an oscillatory migration,...
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Interactions of migrating giant planets and small solar-system bodies
Chrenko, Ondřej ; Brož, Miroslav (advisor)
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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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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