"Barrel Instability" for Elongated Secondaries in Binary Asteroids

2020 ◽  
Author(s):  
Matija Cuk ◽  
Seth Jacobson ◽  
Kevin Walsh
Keyword(s):  
Binary Systems ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Binary Asteroids ◽  
High Eccentricity ◽  
Prolate Shape ◽  
Planetary Satellites ◽  
Synchronous Rotation ◽  
Secondary Line ◽  
Theoretical Results

<p>Most close-in planetary satellites are in synchronous rotation, which is usully the stable end-point of tidal despinning. Saturn's moon Hyperion is a notable exception by having a chaotic rotation. Hyperion's dynamical state is a consequence of its high eccentricity and its highly prolate shape (Wisdom et al. 1984). As many binary asteroids also have elongated secondaries, chaotic rotation is expected for moons in eccentric binaries (Cuk & Nesvorny 2010), and a minority of asteroidal secondaries may be in that state (Pravec et al. 2016). The question of the secondary's rotation is importrant for the action of the BYORP effect, which can quickly evolve orbits of synchrnous (but not non-synchronous) secondaries (Cuk & Burns 2005). Here we report preliminary numerical simulations which indicate that in binary systems with a large secondary and significant spin-orbit coupling a different kind of non-synchronous rotation may arise. In this "barrel instability" the secondary slowly rolls along its long axis, while the longest diameter is staying largelly aligned with the primary-secondary line. This behavior  may be more difficult to detect through lightcurves than a fully chaotic rotation, but would likewise shut down BYORP. Unlike fully chaotic rotation, barrel instability can happen even at low eccentricties. In our presentation we will discuss our theoretical results and their implications for the evolution of binary asteroids, such as the Didymos-Dimorphos pair.</p>

scholarly journals Barrel Instability in Binary Asteroids

2021 ◽  
Vol 2 (6) ◽  
pp. 231
Author(s):  
Matija Ćuk ◽  
Seth A. Jacobson ◽  
Kevin J. Walsh
Keyword(s):  
Numerical Simulations ◽  
Rotational State ◽  
Large Set ◽  
Binary Asteroids ◽  
High Eccentricity ◽  
Earth Asteroid ◽  
Prolate Shape ◽  
Planetary Satellites ◽  
Synchronous Rotation ◽  
Secondary Line

Abstract Most close-in planetary satellites are in synchronous rotation, which is usually the stable end-point of tidal despinning. Saturn’s moon Hyperion is a notable exception by having a chaotic rotation. Hyperion’s dynamical state is a consequence of its high eccentricity and its highly prolate shape. As many binary asteroids also have elongated secondaries, chaotic rotation is expected for moons in eccentric binaries, and a minority of asteroidal secondaries may be in that state. The question of secondary rotation is also important for the action of the binary Yarkovsky–O’Keefe–Radzievskii–Paddack (BYORP) effect, which can quickly evolve orbits of synchronous (but not nonsynchronous) secondaries. Here we report results of a large set of short numerical simulations which indicate that, apart from synchronous and classic chaotic rotation, close-in irregularly shaped asteroidal secondaries can occupy an additional, intermediate rotational state. In this “barrel instability” the secondary slowly rolls along its long axis, while the longest axis is staying largely aligned with the primary–secondary line. This behavior may be more difficult to detect through lightcurves than a fully chaotic rotation, but would likewise shut down BYORP. We show that the binary’s eccentricity, separation measured in secondary’s radii and the secondary’s shape are all important for determining whether the system settles in synchronous rotation, chaotic tumbling, or barrel instability. We compare our results for synthetic asteroids with known binary pairs to determine which of these behaviors may be present in the near-Earth asteroid binary population.

scholarly journals Internal magnetic fields, spin-orbit coupling, and orbital period modulation in close binary systems

2019 ◽  
Author(s):  
A F Lanza
Keyword(s):  
Orbital Period ◽  
Binary Systems ◽  
Orbit Coupling ◽  
Close Binary ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Active Components ◽  
Momentum Exchange ◽  
Hot Jupiters ◽  
Close Binary Systems

Abstract We introduce a new model to explain the modulation of the orbital period observed in close stellar binary systems based on an angular momentum exchange between the spin of the active component and the orbital motion. This spin-orbit coupling is not due to tides, but is produced by a non-axisymmetric component of the gravitational quadrupole moment of the active star due to a persistent non-axisymmetric internal magnetic field. The proposed mechanism easily satisfies all the energy constraints having an energy budget ∼102 − 103 times smaller than those of previously proposed models and is supported by the observations of persistent active longitudes in the active components of close binary systems. We present preliminary applications to three well-studied binary systems to illustrate the model. The case of stars with hot Jupiters is also discussed showing that no significant orbital period modulation is generally expected on the basis of the proposed model.

Study of Electromagnetic Multipole Transition Half-Lives of One-Hole 15O–15N and One-Particle 17O–17F Mirror Nuclei

2013 ◽  
Vol 68 (10-11) ◽  
pp. 709-714 ◽  
Author(s):  
Mohammadreza Pahlavani ◽  
Behnam Firoozi
Keyword(s):  
Experimental Data ◽  
Wave Functions ◽  
The Other ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Matrix Elements ◽  
Saxon Potential ◽  
N Isotopes ◽  
The One ◽  
Theoretical Results

Energy spectrum and wave functions are obtained numerically with a potential consisting of Woods-Saxon, Coulomb, and spin-orbit coupling parts for the nuclei 15O, 15N, 17O, and 17F. The radial parts of the wave functions are used to calculate some matrix elements of electromagnetic transitions. These results are applied to calculate half-lives of low-lying exited states in the one-particle 17O and 17F as well as in the one-hole 15O and 15N isotopes. The calculated half-lives are compared with available experimental and theoretical results based on harmonic oscillator wave functions and Weisskopf units. In comparison with the results calculated from the other methods, our results based on the Woods-Saxon potential indicate a satisfactory agreement with accessible experimental data.

scholarly journals Spin-orbit coupling in binary asteroids

2015 ◽  
Vol 10 (S318) ◽  
pp. 66-68
Author(s):  
Jean-Luc Margot ◽  
Shantanu P. Naidu
Keyword(s):  
Phase Space ◽  
Orbit Coupling ◽  
Spin States ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Binary Asteroids ◽  
Surface Of Section ◽  
Radar Images ◽  
Orbit Dynamics

AbstractWe use radar images with decameter resolution to measure the sizes, shapes, spin states, mutual orbits, masses, and densities of components of asteroid binaries and triples. We simulate the spin-orbit dynamics of these systems and map the possible spin configurations of the satellites on surface of section plots. The presence of chaotic regions in the phase space has important consequences for the evolution of binary asteroids. It may substantially increase spin synchronization timescales, delay BYORP-type evolution, and extend the lifetime of binaries.

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