The Experts below are selected from a list of 7836 Experts worldwide ranked by ideXlab platform

J Klacka - One of the best experts on this subject based on the ideXlab platform.

  • dust grains in mean motion Orbital Resonances with a planet
    Planetary and Space Science, 2020
    Co-Authors: J Klacka, R Nagy, M Jurci
    Abstract:

    Abstract The Orbital evolution of interplanetary dust particles in the Solar System is governed by gravitational and non-gravitational forces. Non-gravitational effects become more significant with decreasing size of dust grains and the effects are relevant on long-time scales. This work considers action of the solar corpuscular radiation in the form of solar wind, solar electromagnetic radiation in the form of the Poynting-Robertson (P-R) effect and gravitational attraction of the Sun and planets. The solar wind influences the evolution of dust grains more significantly than the P-R effect. The paper focuses on mean motion Orbital Resonances of a dust particle with a planet. We deal with the effect of non-gravitational forces in the restricted three body problem and we also investigate the stability of the equilibrium solution. The motion of the dust grain near the equilibrium points L 4 and L 5 can be stable under certain circumstances. The analytical results are also supported by numerical calculations.

  • nonspherical dust grains in mean motion Orbital Resonances
    Astronomy and Astrophysics, 2008
    Co-Authors: Miroslav Kocifaj, J Klacka
    Abstract:

    The effect of stellar electromagnetic radiation on the motion of arbitrarily shaped dust particles in mean-motion Orbital Resonances with planets is investigated. Giving a resonance and a value of parameter β (the ratio between radiation pressure force and gravitational force of the central star), nonradial components of radiation pressure force are calculated when a given trajectory is prescribed. The found values of the nonradial components are in a good agreement with published detailed numerical simulations for a given nonspherical particle. Therefore nonspherical grains are present in mean-motion Resonances with planets. Similarly, the difference between the motion of a real particle and the motion influenced by the Poynting-Robertson effect may be important.

  • effect of radiation on dust particles in Orbital Resonances
    Journal of Quantitative Spectroscopy & Radiative Transfer, 2006
    Co-Authors: J Klacka, Miroslav Kocifaj
    Abstract:

    Abstract The effect of electromagnetic radiation on the dynamics of arbitrarily shaped cosmic dust particles is investigated. The paper concentrates on the motion of dust grains near commensurability Resonances with a planet—mean-motion Resonances—and possible capture of the grains in the Resonances. A particle is in resonance with a planet when the ratio of the mean motions of the two objects is a ratio of two small integers. The most fundamental properties of the Orbital evolution of spherical dust particles in the mean-motion Resonances are shortly rederived: the solar wind effect is also included and the existing result is improved. The results for spherical particles are compared with the detailed numerical calculations for nonspherical particles. It is shown that the fundamental results valid for spherical grains do not hold, in general, for nonspherical particles. While spherical particles are always characterized by the secular decrease of the semi-major axes near mean-motion Resonances, this may not be true for nonspherical particles. Nonspherical grains may exhibit an increase of the semi-major axes before capturing in the mean-motion Resonances. This is caused by the effect of electromagnetic radiation on nonspherical dust grains. The eccentricities of spherical particles in the exterior Resonances approach a limiting value, but nonspherical grains may not follow this behaviour. The interior Resonances are characterized by a systematic decrease of eccentricity for spheres, but various behaviours exist in the case of irregularly shaped particles. The motion of a nonspherical dust particle under the action of electromagnetic radiation may be characterized by a small change of the semi-major axis during a long-time interval, but the particle is not captured in any mean-motion resonance. This kind of motion does not exist for spherical grains.

Man Hoi Lee - One of the best experts on this subject based on the ideXlab platform.

  • diversity and origin of 2 1 Orbital Resonances in extrasolar planetary systems
    The Astrophysical Journal, 2004
    Co-Authors: Man Hoi Lee
    Abstract:

    A diversity of 2 : 1 resonance configurations can be expected in extrasolar planetary systems, and their geometry can provide information about the origin of the Resonances. Assembly during planet formation by the differential migration of planets due to planet-disk interaction is one scenario for the origin of mean-motion Resonances in extrasolar planetary systems. The stable 2 : 1 resonance configurations that can be reached by differential migration of planets with constant masses and initially coplanar and nearly circular orbits are (1) antisymmetric configurations with the mean-motion resonance variables θ1 = λ1 - 2λ2 + 1 and θ2 = λ1 - 2λ2 + 2 (where λj and j are the mean longitudes and the longitudes of periapse, respectively) librating about 0° and 180°, respectively (as in the Io-Europa pair), (2) symmetric configurations with both θ1 and θ2 librating about 0° (as in the GJ 876 system), and (3) asymmetric configurations with θ1 and θ2 librating about angles far from either 0° or 180°. There are, however, stable 2 : 1 resonance configurations with symmetric (θ1 ≈ θ2 ≈ 0°), asymmetric, and antisymmetric (θ1 ≈ 180° and θ2 ≈ 0°) librations that cannot be reached by differential migration of planets with constant masses and initially coplanar and nearly circular orbits. If real systems with these configurations are ever found, their origin would require (1) a change in the planetary mass ratio m1/m2 during migration, (2) a migration scenario involving inclination Resonances, or (3) multiple-planet scattering in crowded planetary systems. We find that the asymmetric configurations with large e2 and the θ1 ≈ 180° and θ2 ≈ 0° configurations have intersecting orbits and that the θ1 ≈ θ2 ≈ 0° configurations with e1 > 0.714 have prograde periapse precessions.

  • diversity and origin of 2 1 Orbital Resonances in extrasolar planetary systems
    arXiv: Astrophysics, 2004
    Co-Authors: Man Hoi Lee
    Abstract:

    (Abridged) A diversity of 2:1 resonance configurations can be expected in extrasolar planetary systems, and their geometry can provide information about the origin of the Resonances. Assembly during planet formation by the differential migration of planets due to planet-disk interaction is one scenario for the origin of mean-motion Resonances in extrasolar planetary systems. The stable 2:1 resonance configurations that can be reached by differential migration of planets with constant masses and initially coplanar and nearly circular orbits are (1) anti-symmetric configurations with the mean-motion resonance variables theta_1 and theta_2 (in deg.) librating about 0 and 180, respectively (as in the Io-Europa pair), (2) symmetric configurations with both theta_1 and theta_2 librating about 0 (as in the GJ 876 system), and (3) asymmetric configurations with theta_1 and theta_2 librating about angles far from either 0 or 180. There are, however, stable 2:1 resonance configurations with symmetric (theta_1 = theta_2 = 0), asymmetric, and anti-symmetric (theta_1 = 180 and theta_2 = 0) librations that cannot be reached by differential migration of planets with constant masses and initially coplanar and nearly circular orbits. If real systems with these configurations are ever found, their origin would require (1) a change in the planetary mass ratio m_1/m_2 during migration, (2) a migration scenario involving inclination Resonances, or (3) multiple-planet scattering in crowded planetary systems. We find that the asymmetric configurations with large e_2 and the theta_1 = 180 and theta_2 = 0 configurations have intersecting orbits and that the theta_1 = theta_2 = 0 configurations with e_1 > 0.714 have prograde periapse precessions.

  • dynamics and origin of the 2 1 Orbital Resonances of the gj 876 planets
    The Astrophysical Journal, 2002
    Co-Authors: Man Hoi Lee, S J Peale
    Abstract:

    The discovery by Marcy and coworkers of two planets in 2 : 1 Orbital resonance about the star GJ 876 has been supplemented by a dynamical fit to the data by Laughlin & Chambers, which places the planets in coplanar orbits deep in three Resonances at the 2 : 1 mean-motion commensurability. The selection of this almost singular state by the dynamical fit means that the Resonances are almost certainly real, and with the small amplitudes of libration of the resonance variables, indefinitely stable. Several unusual properties of the 2 : 1 Resonances are revealed by the GJ 876 system. The libration of both lowest order mean-motion resonance variables and the secular resonance variable, θ1 = λ1 - 2λ2 + 1, θ2 = λ1 - 2λ2 + 2, and θ3 = 1 - 2, about 0° (where λ1,2 are the mean longitudes of the inner and outer planet and 1,2 are the longitudes of periapse) differs from the familiar geometry of the Io-Europa pair, where θ2 and θ3 librate about 180°. By considering the condition that 1 = 2 for stable simultaneous librations of θ1 and θ2, we show that the GJ 876 geometry results from the large Orbital eccentricities ei, whereas the very small eccentricities in the Io-Europa system lead to the latter's geometry. Surprisingly, the GJ 876 configuration, with θ1, θ2, and θ3 all librating, remains stable for e1 up to 0.86 and for amplitude of libration of θ1 approaching 45° with the current eccentricities—further supporting the indefinite stability of the existing system. Any process that drives originally widely separated orbits toward each other could result in capture into the observed Resonances at the 2 : 1 commensurability. We find that forced inward migration of the outer planet of the GJ 876 system results in certain capture into the observed Resonances if initially e1 0.06 and e2 0.03 and the migration rate |2/a2| 3 × 10-2(a2/AU)-3/2 yr-1. Larger eccentricities lead to likely capture into higher order Resonances before the 2 : 1 commensurability is reached. The planets are sufficiently massive to open gaps in the nebular disk surrounding the young GJ 876 and to clear the disk material between them, and the resulting planet-nebular interaction typically forces the outer planet to migrate inward on the disk viscous timescale, whose inverse is about 3 orders of magnitude less than the above upper bound on |2/a2| for certain capture. If there is no eccentricity damping, eccentricity growth is rapid with continued migration within the resonance, with ei exceeding the observed values after a further reduction in the semimajor axes ai of only 7%. With eccentricity damping i/ei = -K|i/ai|, the eccentricities reach equilibrium values that remain constant for arbitrarily long migration within the Resonances. The equilibrium eccentricities are close to the observed eccentricities for K ≈ 100 if there is migration and damping of the outer planet only, but for K ≈ 10 if there is also migration and damping of the inner planet. This result is independent of the magnitude or functional form of the migration rate i as long as i/ei = -K|i/ai|. Although existing analytic estimates of the effects of planet-nebula interaction are consistent with this form of eccentricity damping for certain disk parameter values, it is as yet unclear that such interaction can produce the large value of K required to obtain the observed eccentricities. The alternative eccentricity damping by tidal dissipation within the star or the planets is completely negligible, so the observed dynamical properties of the GJ 876 system may require an unlikely fine-tuning of the time of resonance capture to be near the end of the nebula lifetime.

  • dynamics and origin of the 2 1 Orbital Resonances of the gj 876 planets
    arXiv: Astrophysics, 2001
    Co-Authors: Man Hoi Lee, S J Peale
    Abstract:

    (Abridged) A dynamical fit has placed the two planets about the star GJ 876 in coplanar orbits deep in 3 Resonances at the 2:1 mean-motion commensurability with small libration amplitudes. The libration of both lowest order mean-motion resonance variables, theta_1 and theta_2, and the secular resonance variable, theta_3, about 0 deg. differs from the familiar geometry of the Io-Europa pair, where theta_2 and theta_3 librate about 180 deg. By considering a condition for stable simultaneous librations of theta_1 and theta_2, we show that the GJ 876 geometry results because of the large Orbital eccentricities e_i, whereas the very small e_i in the Io-Europa system lead to the latter's geometry. Surprisingly, the GJ 876 resonance configuration remains stable for e_1 up to 0.86 and for amplitude of libration of theta_1 approaching 45 deg. with the current e_i. We find that inward migration of the outer planet of the GJ 876 system results in certain capture into the observed Resonances if initially e_1 <0.06 and e_2<0.03 and the migration rate |(da_2/dt)/a_2| < 0.03(a_2/AU)^{-3/2} yr^{-1}. The bound on the migration rate is easily satisfied by migration due to planet-nebula interaction. If there is no eccentricity damping, eccentricity growth is rapid with continued migration within the resonance, with e_i exceeding the observed values after a further reduction in the semi-major axes a_i of only 7%. With eccentricity damping (de_i/dt)/e_i = -K|(da_i/dt)/a_i|, the e_i reach equilibrium values that remain constant for arbitrarily long migration within the Resonances. The equilibrium e_i are close to the observed e_i for K=100 (K=10) if there is migration and damping of the outer planet only (of both planets). It is as yet unclear that planet-nebula interaction can produce the large value of K required to obtain the observed eccentricities.

G B Valsecchi - One of the best experts on this subject based on the ideXlab platform.

  • solar radiation pressure Resonances in low earth orbits
    Monthly Notices of the Royal Astronomical Society, 2018
    Co-Authors: Elisa Maria Alessi, Alessandro Rossi, Giulia Schettino, G B Valsecchi
    Abstract:

    The aim of this work is to highlight the crucial role that Orbital Resonances associated with solar radiation pressure can have in Low Earth Orbit. We review the corresponding literature, and provide an analytical tool to estimate the maximum eccentricity which can be achieved for well-defined initial conditions. We then compare the results obtained with the simplified model with the results obtained with a more comprehensive dynamical model. The analysis has important implications both from a theoretical point of view, because it shows that the role of some Resonances was underestimated in the past, but also from a practical point of view in the perspective of passive deorbiting solutions for satellites at the end-of-life.

  • chaos in navigation satellite orbits caused by the perturbed motion of the moon
    Monthly Notices of the Royal Astronomical Society, 2015
    Co-Authors: Aaron J Rosengren, Elisa Maria Alessi, G B Valsecchi, A Rossi
    Abstract:

    ABSTRACT Numerical simulations carried out over the past decade suggest that the orbits of the GlobalNavigation Satellite Systems are unstable, resulting in an apparent chaotic growth of the ec-centricity. Here we show that the irregular and haphazard character of these orbits reflects asimilar irregularity in the orbits of many celestial bodies in our Solar System. We find thatsecular Resonances, involving linear combinations of the frequencies of nodal and apsidal pre-cession and the rate of regression of lunar nodes, occur in profusion so that the phase space isthreaded by a devious stochastic web. As in all cases in the Solar System, chaos ensues whereResonances overlap. These results may be significant for the analysis of disposal strategies forthe four constellations in this precarious region of space.Keywords: celestial mechanics– chaos– methods:analytical–methods :numerical– planetsand satellites: dynamical evolution and stability — planet s and satellites: general. 1 INTRODUCTIONSpace debris—remnants of past missions, satellite explosi ons, andcollisions—is a phenomenon that has existed since the begin ning ofthe space age; however, its significance for space activitie s, in par-ticular the increasing impact risks posed to space systems, has beenrealised only in the past few decades (Kessler & Cour-Palais1978;Rossi et al. 1999; Liou & Johnson 2006). Theproliferation of spacedebris has motivated deeper and more fundamental analysis ofthe long-term evolution of orbits about Earth (Breiter 2001b,a;Celletti & Gales¸ 2014). Orbital Resonances are widespread withinthis system as a whole (Hughes 1980), but particularly so amongstthe medium-Earth orbits (MEOs) of the navigation satellites in theregion of semimajor axes between 4 and 5 Earth radii, and a clearpicture of their nature isof great importance inassessing debris mit-igation measures (Alessi et al. 2014). Indeed, the discovery that therecommended graveyard orbits of these satellites, located severalhundred kilometres above the operational constellations, are poten-tiallyunstable has led toa new paradigm in post-mission disposal—one that seeks to cleverly exploit these dynamical instabilitiesand the associated eccentricity growth for re-entry and destructionwithin the Earth’s atmosphere (Jenkin & Gick 2002; Chao & Gick2004; Rossi 2008; Deleflie et al. 2011). Previous studies hav e al-ready noted theconnection between theorigin of the long-timescaleinstabilities in the MEO region and a resonance phenomenon in-volving Earth oblateness and lunisolar perturbations, yet very littleattention has been given to a true physical explanation of the erratic

Miroslav Kocifaj - One of the best experts on this subject based on the ideXlab platform.

  • nonspherical dust grains in mean motion Orbital Resonances
    Astronomy and Astrophysics, 2008
    Co-Authors: Miroslav Kocifaj, J Klacka
    Abstract:

    The effect of stellar electromagnetic radiation on the motion of arbitrarily shaped dust particles in mean-motion Orbital Resonances with planets is investigated. Giving a resonance and a value of parameter β (the ratio between radiation pressure force and gravitational force of the central star), nonradial components of radiation pressure force are calculated when a given trajectory is prescribed. The found values of the nonradial components are in a good agreement with published detailed numerical simulations for a given nonspherical particle. Therefore nonspherical grains are present in mean-motion Resonances with planets. Similarly, the difference between the motion of a real particle and the motion influenced by the Poynting-Robertson effect may be important.

  • effect of radiation on dust particles in Orbital Resonances
    Journal of Quantitative Spectroscopy & Radiative Transfer, 2006
    Co-Authors: J Klacka, Miroslav Kocifaj
    Abstract:

    Abstract The effect of electromagnetic radiation on the dynamics of arbitrarily shaped cosmic dust particles is investigated. The paper concentrates on the motion of dust grains near commensurability Resonances with a planet—mean-motion Resonances—and possible capture of the grains in the Resonances. A particle is in resonance with a planet when the ratio of the mean motions of the two objects is a ratio of two small integers. The most fundamental properties of the Orbital evolution of spherical dust particles in the mean-motion Resonances are shortly rederived: the solar wind effect is also included and the existing result is improved. The results for spherical particles are compared with the detailed numerical calculations for nonspherical particles. It is shown that the fundamental results valid for spherical grains do not hold, in general, for nonspherical particles. While spherical particles are always characterized by the secular decrease of the semi-major axes near mean-motion Resonances, this may not be true for nonspherical particles. Nonspherical grains may exhibit an increase of the semi-major axes before capturing in the mean-motion Resonances. This is caused by the effect of electromagnetic radiation on nonspherical dust grains. The eccentricities of spherical particles in the exterior Resonances approach a limiting value, but nonspherical grains may not follow this behaviour. The interior Resonances are characterized by a systematic decrease of eccentricity for spheres, but various behaviours exist in the case of irregularly shaped particles. The motion of a nonspherical dust particle under the action of electromagnetic radiation may be characterized by a small change of the semi-major axis during a long-time interval, but the particle is not captured in any mean-motion resonance. This kind of motion does not exist for spherical grains.

D P Hamilton - One of the best experts on this subject based on the ideXlab platform.

  • Orbital Resonances in the inner neptunian system ii resonant history of proteus larissa galatea and despina
    Icarus, 2008
    Co-Authors: Ke Zhang, D P Hamilton
    Abstract:

    We investigate the Orbital history of the small neptunian satellites discovered by Voyager 2. Over the age of the Solar System, tidal forces have caused the satellites to migrate radially, bringing them through mean-motion Resonances with one another. In this paper, we extend our study of the largest satellites Proteus and Larissa [Zhang, K., Hamilton, D.P., 2007. Icarus 188, 386–399] by adding in mid-sized Galatea and Despina. We test the hypothesis that these moons all formed with zero inclinations, and that Orbital Resonances excited their tilts during tidal migration. We find that the current Orbital inclinations of Proteus, Galatea, and Despina are consistent with resonant excitation if they have a common density 0.4 < ¯ ρ< 0. 8g /cm 3 . Larissa’s inclination, however, is too large to have been caused by resonant kicks between these four satellites; we suggest that a prior resonant capture event involving either Naiad or Thalassa is responsible. Our solution requires at least three past Resonances with Proteus, which helps constrain the tidal migration timescale and thus Neptune’s tidal quality factor: 9000 Orbital evolution around an oblate primary. Published by Elsevier Inc.

  • Orbital Resonances in the inner neptunian system i the 2 1 proteus larissa mean motion resonance
    Icarus, 2007
    Co-Authors: Ke Zhang, D P Hamilton
    Abstract:

    We investigate the Orbital resonant history of Proteus and Larissa, the two largest inner neptunian satellites discovered by Voyager 2 .D ue to tidal migration, these two satellites probably passed through their 2:1 mean-motion resonance a few hundred million years ago. We explore this resonance passage as a method to excite Orbital eccentricities and inclinations, and find interesting constraints on the satellites’ mean density (0.05 g/cm 3 10). Through numerical study of this mean-motion resonance passage, we identify a new type of three-body resonance between the satellite pair and Triton. These new Resonances occur near the traditional two-body Resonances between the small satellites and, surprisingly, are much stronger than their two-body counterparts due to Triton’s large mass and Orbital inclination. We determine the relevant resonant arguments and derive a mathematical framework for analyzing Resonances in this special system.