scholarly journals Tidal distortion and disruption of rubble-pile bodies revisited

2020 ◽  
Vol 640 ◽  
pp. A102
Author(s):  
Yun Zhang ◽  
Patrick Michel
Keyword(s):  
Small Body ◽  
Influence Factors ◽  
Dynamical Evolution ◽  
Continuum Theory ◽  
Close Approach ◽  
Material Strength ◽  
Discrete Element Modeling ◽  
Small Bodies ◽  
Tidal Forces ◽  
Rubble Pile

Context. In the course of a close approach to planets or stars, the morphological and dynamical properties of rubble-pile small bodies can be dramatically modified, and some may catastrophically break up, as in the case of comet Shoemaker-Levy 9. This phenomenon is of particular interest for the understanding of the evolution and population of small bodies, and for making predictions regarding the outcomes of future encounters. Previous numerical explorations have typically used methods that do not adequately represent the nature of rubble piles. The encounter outcomes and influence factors are still poorly constrained. Aims. Based on recent advances in modeling rubble-pile physics, we aim to provide a better understanding of the tidal encounter processes of rubble piles through soft-sphere discrete element modeling (SSDEM) and to establish a database of encounter outcomes and their dependencies on encounter conditions and rubble-pile properties. Methods. We performed thousands of numerical simulations using the SSDEM implemented in the N-body code pkdgrav to study the dynamical evolution of rubble piles during close encounters with the Earth. The effects of encounter conditions, material strength, arrangement, and resolution of constituent particles are explored. Results. Three typical tidal encounter outcomes are classified, namely: deformation, mass shedding, and disruption, ranging from mild modifications to severe damages of the progenitor. The outcome is highly dependent on the encounter conditions and on the structure and strength of the involved rubble pile. The encounter speed and distance required for causing disruption events are much smaller than those predicted by previous studies, indicating a smaller creation rate of tidally disrupted small body populations. Extremely elongated fragments with axis ratios ~1:6 can be formed by moderate tidal encounters. Our analyses of the spin-shape evolution of the largest remnants reveal reshaping mechanisms of rubble piles in response to tidal forces, which is consistent with stable rubble-pile configurations derived by continuum theory. A case study for Shoemaker-Levy 9 suggests a low bulk density (0.2–0.3 g cc−1) for its progenitor.

scholarly journals Tidal disturbances of small cohesionless bodies: limits on planetary close approach distances

2006 ◽  
Vol 2 (S236) ◽  
pp. 201-210
Author(s):  
Patrick Michel ◽  
K. A. Holsapple
Keyword(s):  
Bulk Density ◽  
Close Approach ◽  
General Concept ◽  
Material Strength ◽  
Small Bodies ◽  
Tidal Forces ◽  
Planetary Satellites ◽  
Real Objects ◽  
Definition Of ◽  
Asteroids And Comets

AbstractThe population of Near-Earth Objects contains small bodies that can make very close passages to the Earth and the other planets. Depending on the approach distance and the object's internal structure, some shape readjustment or disruption may occur as a result of tidal forces. A real example is the comet Shoemaker Levy 9 which disrupted into 21 fragments as a result of a close approach to Jupiter, before colliding with the planet during the next passage in July 1994. We have recently developed an exact analytical theory for the distortion and disruption limits of spinning ellipsoidal bodies subjected to tidal forces, using the Drucker-Prager strength model with zero cohesion. This model is the appropriate one for dry granular materials such as sands and rocks, for rubble-pile asteroids and comets, as well as for larger planetary satellites, asteroids and comets for which the cohesion can be ignored. Here, we recall the general concept of this theory for which details and major results are given in a recent publication. In particular, we focus on the definition of “material strength”: while it has great implications this concept is often misunderstood in the community of researchers working on small bodies. Then, we apply our theory to a few real objects, showing that it can provide some constraints on their unknown properties such as their bulk density. In particular it can be used to estimate the maximum bulk density that a particular object, such as 99942 Apophis, must have to undergo some tidal readjustments during a predicted planetary approach. The limits of this theory are also discussed. The cases where internal cohesion cannot be ignored will then be investigated in the near future.

scholarly journals Autonomous Exploration of Small Bodies Toward Greater Autonomy for Deep Space Missions

2021 ◽  
Vol 8 ◽  
Author(s):  
Issa A. D. Nesnas ◽  
Benjamin J. Hockman ◽  
Saptarshi Bandopadhyay ◽  
Benjamin J. Morrell ◽  
Daniel P. Lubey ◽  
...  
Keyword(s):  
Feature Tracking ◽  
Rotation Axis ◽  
Small Body ◽  
A Priori ◽  
Reconstruction Algorithm ◽  
Close Approach ◽  
Shape Reconstruction ◽  
The Body ◽  
Body Motion ◽  
Small Bodies

Autonomy is becoming increasingly important for the robotic exploration of unpredictable environments. One such example is the approach, proximity operation, and surface exploration of small bodies. In this article, we present an overview of an estimation framework to approach and land on small bodies as a key functional capability for an autonomous small-body explorer. We use a multi-phase perception/estimation pipeline with interconnected and overlapping measurements and algorithms to characterize and reach the body, from millions of kilometers down to its surface. We consider a notional spacecraft design that operates across all phases from approach to landing and to maneuvering on the surface of the microgravity body. This SmallSat design makes accommodations to simplify autonomous surface operations. The estimation pipeline combines state-of-the-art techniques with new approaches to estimating the target’s unknown properties across all phases. Centroid and light-curve algorithms estimate the body–spacecraft relative trajectory and rotation, respectively, using a priori knowledge of the initial relative orbit. A new shape-from-silhouette algorithm estimates the pole (i.e., rotation axis) and the initial visual hull that seeds subsequent feature tracking as the body gets more resolved in the narrow field-of-view imager. Feature tracking refines the pole orientation and shape of the body for estimating initial gravity to enable safe close approach. A coarse-shape reconstruction algorithm is used to identify initial landable regions whose hazardous nature would subsequently be assessed by dense 3D reconstruction. Slope stability, thermal, occlusion, and terra-mechanical hazards would be assessed on densely reconstructed regions and continually refined prior to landing. We simulated a mission scenario for approaching a hypothetical small body whose motion and shape were unknown a priori, starting from thousands of kilometers down to 20 km. Results indicate the feasibility of recovering the relative body motion and shape solely relying on onboard measurements and estimates with their associated uncertainties and without human input. Current work continues to mature and characterize the algorithms for the last phases of the estimation framework to land on the surface.

scholarly journals Post-rendezvous radar properties of comet 67P/CG from the Rosetta Mission: understanding future Earth-based radar observations and the dynamical evolution of comets

2019 ◽  
Vol 489 (2) ◽  
pp. 1667-1683 ◽  
Author(s):  
Essam Heggy ◽  
Elizabeth M Palmer ◽  
Alain Hérique ◽  
Wlodek Kofman ◽  
M Ramy El-Maarry
Keyword(s):  
Large Scale ◽  
Structural Changes ◽  
Dynamical Evolution ◽  
Textural Properties ◽  
Building Blocks ◽  
Cometary Nucleus ◽  
Small Scale ◽  
Small Bodies ◽  
Radar Observations ◽  
Comet 67P

ABSTRACT Radar observations provide crucial insights into the formation and dynamical evolution of comets. This ability is constrained by our knowledge of the dielectric and textural properties of these small-bodies. Using several observations by Rosetta as well as results from the Earth-based Arecibo radio telescope, we provide an updated and comprehensive dielectric and roughness description of Comet 67P/CG, which can provide new constraints on the radar properties of other nuclei. Furthermore, contrary to previous assumptions of cometary surfaces being dielectrically homogeneous and smooth, we find that cometary surfaces are dielectrically heterogeneous ( εr′≈1.6–3.2), and are rough at X- and S-band frequencies, which are widely used in characterization of small-bodies. We also investigate the lack of signal broadening in CONSERT observations through the comet head. Our results suggest that primordial building blocks in the subsurface are either absent, smaller than the radar wavelength, or have a weak dielectric contrast (Δ εr′). To constrain this ambiguity, we use optical albedo measurements by the OSIRIS camera of the freshly exposed subsurface after the Aswan cliff collapse. We find that the hypothetical subsurface blocks should have |Δ εr′|≳0.15, setting an upper limit of ∼ 1 m on the size of 67P/CG's primordial building blocks if they exist. Our analysis is consistent with a purely thermal origin for the ∼ 3 m surface bumps on pit walls and cliff-faces, hypothesized to be high-centred polygons formed from fracturing of the sintered shallow ice-bearing subsurface due to seasonal thermal expansion and contraction. Potential changes in 67P/CG's radar reflectivity at these at X- and S-bands can be associated with large-scale structural changes of the nucleus rather than small-scale textural ones. Monitoring changes in 67P/CG's radar properties during repeated close-approaches via Earth-based observations can constrain the dynamical evolution of its cometary nucleus.

scholarly journals DYNAMICAL DERIVATION OF BODE'S LAW

2005 ◽  
Vol 14 (01) ◽  
pp. 153-169 ◽  
Author(s):  
R. W. BASS ◽  
A. DEL POPOLO
Keyword(s):  
Angular Momentum ◽  
Total Angular Momentum ◽  
Central Body ◽  
Dynamical Evolution ◽  
Satellite System ◽  
Point Particle ◽  
The Body ◽  
The Sun ◽  
Small Bodies ◽  
Orbital Radius

In a planetary or satellite system, idealized as n small bodies in an initially coplanar with concentric orbits around a large central body obeying the Newtonian point-particle mechanics, resonant perturbations will cause a dynamical evolution of the orbital radii except for cases with highly specific mutual relationships. In particular, the most stable situation can be achieved only when each planetary orbit is roughly twice as far from the Sun as the preceding one. This has been empirically observed by Titius (1766) and Bode (1778). By reformulating the problem as a hierarchical sequence of (unrestricted) 3-body problems and considering only the gravitational interactions among the central body and the body of interest and the adjacent outer body in the orbits, it is proved that the resonant perturbations from the outer body will destabilize the inner body (and vice versa) unless its mean orbital radius is a unique and specific multiple of β, the distal multiplier, of the inner body. In this way a sequence of concentric orbits can each stabilize the adjacent inner orbit, and since the outermost orbit is already tied to the collection of the inner orbits by conservation of total angular momentum, the entire configuration is stabilized.

scholarly journals Orbital features of distant trans-Neptunian objects induced by giant gaseous clumps

2020 ◽  
Vol 642 ◽  
pp. L20
Author(s):  
V. V. Emel’yanenko
Keyword(s):  
Simple Model ◽  
Solar Nebula ◽  
Dynamical Evolution ◽  
Outer Solar System ◽  
The Sun ◽  
High Eccentricity ◽  
Small Bodies ◽  
Dynamical Characteristics ◽  
Gravitational Perturbations ◽  
The Hill

Context. The discovery of distant trans-Neptunian objects has led to heated discussions about the structure of the outer Solar System. Aims. We study the dynamical evolution of small bodies from the Hill regions of migrating giant gaseous clumps that form in the outer solar nebula via gravitational fragmentation. We attempt to determine whether the observed features of the orbital distribution of distant trans-Neptunian objects could be caused by this process. Methods. We consider a simple model that includes the Sun, two point-like giant clumps with masses of ∼10 Jupiter masses, and a set of massless objects initially located in the Hill regions of these clumps. We carry out numerical simulations of the motions of small bodies under gravitational perturbations from two giant clumps that move in elliptical orbits and approach each other. The orbital distribution of these small bodies is compared with the observed distribution of distant trans-Neptunian objects. Results. In addition to the known grouping in longitudes of perihelion, we note new features for observed distant trans-Neptunian objects. The observed orbital distribution points to the existence of two groups of distant trans-Neptunian objects with different dynamical characteristics. We show that the main features of the orbital distribution of distant trans-Neptunian objects can be explained by their origin in the Hill regions of migrating giant gaseous clumps. Small bodies are ejected from the Hill regions when the giant clumps move in high-eccentricity orbits and have a close encounter with each other. Conclusions. The resulting orbital distribution of small bodies in our model and the observed distribution of distant trans-Neptunian objects have similar features.

scholarly journals Accretion of eroding pebbles and planetesimals in planetary envelopes

2020 ◽  
Vol 641 ◽  
pp. A99
Author(s):  
Tunahan Demirci ◽  
Gerhard Wurm
Keyword(s):  
Wind Erosion ◽  
Small Body ◽  
Major Axis ◽  
Minor Importance ◽  
Semi Major Axis ◽  
Weakly Bound ◽  
Small Bodies ◽  
Planetary Body ◽  
Threshold Size ◽  
Threshold Radius

Wind erosion is a destructive mechanism that completely dissolves a weakly bound object like a planetesimal into its constituent particles, if the velocity relative to the ambient gas and the local gas pressure are sufficiently high. In numerical simulations we study the influence of such wind erosion on pebble and planetesimal accretion by a planetary body up to 10 REarth. Due to the rapid size reduction of an in-falling small body, the accretion outcome changes significantly. Erosion leads to a strong decrease in the accretion efficiency below a threshold size of the small body on the order of 10 m. This slows down pebble accretion significantly for a given size distribution of small bodies. The threshold radius of the small body increases with increasing planet radius and decreases with increasing semi-major axis. Within the parameters studied, an additional planetary atmosphere (up to 1 bar) is of minor importance.

scholarly journals The Locations of Secular Resonances and the Evolution of Small Solar System Bodies

1992 ◽  
Vol 152 ◽  
pp. 123-132
Author(s):  
Ch Froeschle ◽  
P. Farinella ◽  
C. Froeschle ◽  
Z. Knežević ◽  
A. Milani
Keyword(s):  
Perturbation Theory ◽  
Solar System ◽  
Small Body ◽  
Kuiper Belt ◽  
Dynamical Evolution ◽  
Asteroid Belt ◽  
Secular Resonances ◽  
Outer Planets ◽  
Proper Elements ◽  
Solar System Bodies

Generalizing the secular perturbation theory of Milani and Knežević (1990), we have determined in the a — e — I proper elements space the locations of the secular resonances between the precession rates of the longitudes of perihelion and node of a small body and the corresponding eigenfrequencies of the secular perturbations of the four outer planets. We discuss some implications of the results for the dynamical evolution of small solar system bodies. In particular, our findings include: (i) the fact that the g = g6 resonance in the inner asteroid belt lies closer than previously assumed to the Flora region, providing a plausible dynamical route to inject asteroid fragments into planet-crossing orbits; (ii) the possible presence of some low-inclination “stable islands” between the orbits of the outer planets; (iii) the fact that none of the secular resonances considered in this work exists for semimajor axes > 50 AU, so that these resonances do not provide a mechanism for transporting inwards possible Kuiper–belt comets.

scholarly journals Dynamical Evolution of Stellar Clusters and Associations in the Field of Tidal Forces of the Galaxy

1993 ◽  
Vol 132 ◽  
pp. 183-192 ◽  
Author(s):  
T.S. Kozhanov
Keyword(s):  
Jacobi Equation ◽  
Equations Of Motion ◽  
Dynamical Evolution ◽  
Stellar Clusters ◽  
Many Body ◽  
Tidal Forces ◽  
Elliptic Orbits ◽  
The Galaxy ◽  
The Moment ◽  
The Many

AbstractThe equations of motion of the star-members of the cluster averaged on the elliptic orbits are obtained. These equations take into account the tidal forces of the Galaxy. The generalization of the Lagrange-Jacobi equation and Sundman inequality for non-classical scheme of the many-body problems is revised. The dynamical evolution of the moment of inertia is studied. Some theorems which determine the type of the star motion in the cluster are formulated.

scholarly journals Dynamical evolution of two-planet systems and its connection with white dwarf atmospheric pollution

2020 ◽  
Vol 497 (4) ◽  
pp. 4091-4106 ◽  
Author(s):  
R F Maldonado ◽  
E Villaver ◽  
A J Mustill ◽  
M Chavez ◽  
E Bertone
Keyword(s):  
Atmospheric Pollution ◽  
Ad Hoc ◽  
Planetary Systems ◽  
Dynamical Evolution ◽  
Asymptotic Giant Branch ◽  
Dynamical Instability ◽  
System Architectures ◽  
Tidal Forces ◽  
Eccentric Orbits ◽  
Current Paradigm

ABSTRACT Asteroid material is detected in white dwarfs (WDs) as atmospheric pollution by metals, in the form of gas/dust discs, or in photometric transits. Within the current paradigm, minor bodies need to be scattered, most likely by planets, into highly eccentric orbits where the material gets disrupted by tidal forces and then accreted on to the star. This can occur through a planet–planet scattering process triggered by the stellar mass-loss during the post main-sequence (MS) evolution of planetary systems. So far, studies of the N-body dynamics of this process have used artificial planetary system architectures built ad hoc. In this work, we attempt to go a step further and study the dynamical instability provided by more restrictive systems that, at the same time, allow us an exploration of a wider parameter space: the hundreds of multiple planetary systems found around MS stars. We find that most of our simulated systems remain stable during the MS, Red, and Asymptotic Giant Branch and for several Gyr into the WD phases of the host star. Overall, only ≈2.3 ${{\ \rm per\ cent}}$ of the simulated systems lose a planet on the WD as a result of dynamical instability. If the instabilities take place during the WD phase most of them result in planet ejections with just five planetary configurations ending as a collision of a planet with the WD. Finally 3.2 ${{\ \rm per\ cent}}$ of the simulated systems experience some form of orbital scattering or orbit crossing that could contribute to the pollution at a sustained rate if planetesimals are present in the same system.

scholarly journals The collision between the Milky Way and Andromeda and the fate of their Supermassive Black Holes

2019 ◽  
Vol 14 (S351) ◽  
pp. 161-164 ◽  
Author(s):  
Riccardo Schiavi ◽  
Roberto Capuzzo-Dolcetta ◽  
Manuel Arca Sedda ◽  
Mario Spera
Keyword(s):  
Black Holes ◽  
Velocity Vector ◽  
Milky Way ◽  
Orbital Motion ◽  
Initial Conditions ◽  
Dynamical Evolution ◽  
Close Approach ◽  
Supermassive Black Holes ◽  
Andromeda Galaxy ◽  
Proper Resolution

AbstractOur Galaxy and the nearby Andromeda Galaxy (M31) form a bound system, even though the relative velocity vector of M31 is currently not well constrained. Their orbital motion is highly dependent on the initial conditions, but all the reliable scenarios imply a first close approach in the next 3–5 Gyrs. In our study, we simulate this interaction via direct N-body integration, using the HiGPUs code. Our aim is to investigate the dependence of the time of the merger on the physical and dynamical properties of the system. Finally, we study the dynamical evolution of the two Supermassive Black Holes placed in the two galactic centers, with the future aim to achieve a proper resolution to follow their motion until they form a tight binary system.

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