The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Fred C. Adams - One of the best experts on this subject based on the ideXlab platform.
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Evolution of Planetary Orbits with Stellar Mass Loss and Tidal Dissipation
The Astrophysical Journal, 2013Co-Authors: Fred C. Adams, Anthony M. BlochAbstract:Intermediate mass stars and stellar remnants often host planets, and these dynamical systems evolve because of mass loss and tides. This paper considers the combined action of stellar mass loss and tidal dissipation on Planetary Orbits in order to determine the conditions required for Planetary survival. Stellar mass loss is included using a so-called Jeans model, described by a dimensionless mass loss rate \gamma and an index \beta. We use an analogous prescription to model tidal effects, described here by a dimensionless dissipation rate \Gamma and two indices (q,p). The initial conditions are determined by the starting value of angular momentum parameter \eta (equivalently, the initial eccentricity) and the phase \theta of the orbit. Within the context of this model, we derive an analytic formula for the critical dissipation rate \Gamma, which marks the boundary between Orbits that spiral outward due to stellar mass loss and those that spiral inward due to tidal dissipation. This analytic result \Gamma=\Gamma(\gamma,\beta,q,p,\eta,\theta) is essentially exact for initially circular Orbits and holds to within an accuracy of 50% over the entire multi-dimensional parameter space, where the individual parameters vary by several orders of magnitude. For stars that experience mass loss, the stellar radius often displays quasi-periodic variations, which produce corresponding variations in tidal forcing; we generalize the calculation to include such pulsations using a semi-analytic treatment that holds to the same accuracy as the non-pulsating case. These results can be used in many applications, e.g., to predict/constrain properties of Planetary systems orbiting white dwarfs.
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evolution of Planetary Orbits with stellar mass loss and tidal dissipation
The Astrophysical Journal, 2013Co-Authors: Fred C. Adams, Anthony M. BlochAbstract:Intermediate mass stars and stellar remnants often host planets, and these dynamical systems evolve because of mass loss and tides. This paper considers the combined action of stellar mass loss and tidal dissipation on Planetary Orbits in order to determine the conditions required for Planetary survival. Stellar mass loss is included using a so-called Jeans model, described by a dimensionless mass loss rate γ and an index β. We use an analogous prescription to model tidal effects, described here by a dimensionless dissipation rate Γ and two indices (q, p). The initial conditions are determined by the starting value of angular momentum parameter η0 (equivalently, the initial eccentricity) and the phase θ of the orbit. Within the context of this model, we derive an analytic formula for the critical dissipation rate Γ, which marks the boundary between Orbits that spiral outward due to stellar mass loss and those that spiral inward due to tidal dissipation. This analytic result Γ = Γ(γ, β, q, p, η0, θ) is essentially exact for initially circular Orbits and holds to within an accuracy of ≈50% over the entire multi-dimensional parameter space, where the individual parameters vary by several orders of magnitude. For stars that experience mass loss, the stellar radius often displays quasi-periodic variations, which produce corresponding variations in tidal forcing; we generalize the calculation to include such pulsations using a semi-analytic treatment that holds to the same accuracy as the non-pulsating case. These results can be used in many applications, e.g., to predict/constrain properties of Planetary systems orbiting white dwarfs.
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dynamical stability of earth like Planetary Orbits in binary systems
Publications of the Astronomical Society of the Pacific, 2003Co-Authors: Evamarie David, Elisa V Quintana, Marco Fatuzzo, Fred C. AdamsAbstract:This paper explores the stability of an Earth-like planet orbiting a solar-mass star in the presence of an outer-lying intermediate-mass companion. The overall goal is to estimate the fraction of binary systems that allow Earth-like planets to remain stable over long timescales. We numerically determine the planet's ejection time tej over a range of companion masses ( ), orbital eccentricities e, and semimajor axes M p 0.001-0.5 M C , a. This suite of ∼40,000 numerical experiments suggests that the most important variables are the companion's mass and periastron distance to the primary star. At fixed , the ejection time is a steeply MR p a(1 e) M C min C increasing function of over the range of parameter space considered here (although the ejection time has a Rmin distribution of values for a given ). Most of the integration times are limited to 10 Myr, but a small set of Rmin integrations extend to 500 Myr. For each companion mass, we find fitting formulae that approximate the mean ejection time as a function of . These functions can then be extrapolated to longer timescales. By combining Rmin the numerically determined ejection times with the observed distributions of orbital parameters for binary systems, we estimate that (at least) 50% of binaries allow an Earth-like planet to remain stable over the 4.6 Gyr age of our solar system.
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dynamical stability of earth like Planetary Orbits in binary systems
arXiv: Astrophysics, 2003Co-Authors: Evamarie David, Elisa V Quintana, Marco Fatuzzo, Fred C. AdamsAbstract:This paper explores the stability of an Earth-like planet orbiting a solar mass star in the presence of an outer-lying intermediate mass companion. The overall goal is to estimate the fraction of binary systems that allow Earth-like planets to remain stable over long time scales. We numerically determine the planet's ejection time $\tauej$ over a range of companion masses ($M_C$ = 0.001 -- 0.5 $M_\odot$), orbital eccentricities $\epsilon$, and semi-major axes $a$. This suite of $\sim40,000$ numerical experiments suggests that the most important variables are the companion's mass $M_C$ and periastron distance $\rmin$ = $a(1-\epsilon)$ to the primary star. At fixed $M_C$, the ejection time is a steeply increasing function of $\rmin$ over the range of parameter space considered here (although the ejection time has a distribution of values for a given $\rmin$). Most of the integration times are limited to 10 Myr, but a small set of integrations extend to 500 Myr. For each companion mass, we find fitting formulae that approximate the mean ejection time as a function of $\rmin$. These functions can then be extrapolated to longer time scales. By combining the numerically determined ejection times with the observed distributions of orbital parameters for binary systems, we estimate that (at least) 50 percent of binaries allow an Earth-like planet to remain stable over the 4.6 Gyr age of our solar system.
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Astronomical Engineering: A Strategy For Modifying Planetary Orbits
Astrophysics and Space Science, 2001Co-Authors: D.g. Korycansky, Gregory Laughlin, Fred C. AdamsAbstract:The Sun's gradual brightening will seriously compromise the Earth'sbiosphere within ∼ 10^9 years. If Earth's orbit migrates outward,however, the biosphere could remain intact over the entiremain-sequence lifetime of the Sun. In this paper, we explore thefeasibility of engineering such a migration over a long timeperiod. The basic mechanism uses gravitational assists to (in effect)transfer orbital energy from Jupiter to the Earth, and therebyenlarges the orbital radius of Earth. This transfer is accomplishedby a suitable intermediate body, either a Kuiper Belt object or a mainbelt asteroid. The object first encounters Earth during an inward passon its initial highly elliptical orbit of large (∼ 300 AU)semimajor axis. The encounter transfers energy from the object to theEarth in standard gravity-assist fashion by passing close to theleading limb of the planet. The resulting outbound trajectory of theobject must cross the orbit of Jupiter; with proper timing, theoutbound object encounters Jupiter and picks up the energy it lost toEarth. With small corrections to the trajectory, or additionalPlanetary encounters (e.g., with Saturn), the object can repeat thisprocess over many encounters. To maintain its present flux of solarenergy, the Earth must experience roughly one encounter every 6000years (for an object mass of 10^22 g). We develop the details ofthis scheme and discuss its ramifications.
Konstantin Batygin - One of the best experts on this subject based on the ideXlab platform.
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chaotic disintegration of the inner solar system
The Astrophysical Journal, 2015Co-Authors: Konstantin Batygin, Alessandro Morbidelli, Matthew J HolmanAbstract:On timescales that greatly exceed an orbital period, typical Planetary Orbits evolve in a stochastic yet stable fashion. On even longer timescales, however, Planetary Orbits can spontaneously transition from bounded to unbound chaotic states. Large-scale instabilities associated with such behavior appear to play a dominant role in shaping the architectures of Planetary systems, including our own. Here we show how such transitions are possible, focusing on the specific case of the long-term evolution of Mercury. We develop a simple analytical model for Mercury's dynamics and elucidate the origins of its short-term stochastic behavior as well as of its sudden progression to unbounded chaos. Our model allows us to estimate the timescale on which this transition is likely to be triggered, i.e., the dynamical lifetime of the solar system as we know it. The formulated theory is consistent with the results of numerical simulations and is broadly applicable to extrasolar Planetary systems dominated by secular interactions. These results constitute a significant advancement in our understanding of the processes responsible for sculpting of the dynamical structures of generic Planetary systems.
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A Primordial Origin for Misalignments Between Stellar Spin Axes and Planetary Orbits
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: Konstantin BatyginAbstract:The presence of gaseous giant planets whose Orbits lie in extreme proximity to their host stars ("hot Jupiters"), can largely be accounted for by Planetary migration, associated with viscous evolution of proto-Planetary nebulae. Recently, observations of the Rossiter-McLaughlin effect during Planetary transits have revealed that a considerable fraction of detected hot Jupiters reside on Orbits that are misaligned with respect to the spin-axes of their host stars. This observational fact has cast significant doubts on the importance of disk-driven migration as a mechanism for production of hot Jupiters, thereby reestablishing the origins of close-in Planetary Orbits as an open question. Here we show that misaligned Orbits can be a natural consequence of disk migration. Our argument rests on an enhanced abundance of binary stellar companions in star formation environments, whose orbital plane is uncorrelated with the spin axes of the individual stars. We analyze the dynamical evolution of idealized proto-Planetary disks under perturbations from massive distant bodies and demonstrate that the resulting gravitational torques act to misalign the orbital planes of the disks relative to the spin poles of their host stars. As a result, we predict that in the absence of strong disk-host star angular momentum coupling or sufficient dissipation that acts to realign the stellar spin axis and the Planetary Orbits, the fraction of Planetary systems (including systems of hot Neptunes and Super-Earths), whose angular momentum vectors are misaligned with respect to their host-stars should be commensurate with the rate of primordial stellar multiplicity.
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A primordial origin for misalignments between stellar spin axes and Planetary Orbits.
Nature, 2012Co-Authors: Konstantin BatyginAbstract:The existence of gaseous giant planets whose Orbits lie close to their host stars ('hot Jupiters') can largely be accounted for by Planetary migration associated with viscous evolution of proto-Planetary nebulae. Recently, observations of the Rossiter-McLaughlin effect during Planetary transits have revealed that a considerable fraction of hot Jupiters are on Orbits that are misaligned with respect to the spin axes of their host stars. This observation has cast doubt on the importance of disk-driven migration as a mechanism for producing hot Jupiters. Here I show that misaligned Orbits can be a natural consequence of disk migration in binary systems whose orbital plane is uncorrelated with the spin axes of the individual stars. The gravitational torques arising from the dynamical evolution of idealized proto-Planetary disks under perturbations from massive distant bodies act to misalign the orbital planes of the disks relative to the spin poles of their host stars. As a result, I suggest that in the absence of strong coupling between the angular momentum of the disk and that of the host star, or of sufficient dissipation that acts to realign the stellar spin axis and the Planetary Orbits, the fraction of Planetary systems (including systems of 'hot Neptunes' and 'super-Earths') whose angular momentum vectors are misaligned with respect to their host stars will be commensurate with the rate of primordial stellar multiplicity.
Anthony M. Bloch - One of the best experts on this subject based on the ideXlab platform.
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Evolution of Planetary Orbits with Stellar Mass Loss and Tidal Dissipation
The Astrophysical Journal, 2013Co-Authors: Fred C. Adams, Anthony M. BlochAbstract:Intermediate mass stars and stellar remnants often host planets, and these dynamical systems evolve because of mass loss and tides. This paper considers the combined action of stellar mass loss and tidal dissipation on Planetary Orbits in order to determine the conditions required for Planetary survival. Stellar mass loss is included using a so-called Jeans model, described by a dimensionless mass loss rate \gamma and an index \beta. We use an analogous prescription to model tidal effects, described here by a dimensionless dissipation rate \Gamma and two indices (q,p). The initial conditions are determined by the starting value of angular momentum parameter \eta (equivalently, the initial eccentricity) and the phase \theta of the orbit. Within the context of this model, we derive an analytic formula for the critical dissipation rate \Gamma, which marks the boundary between Orbits that spiral outward due to stellar mass loss and those that spiral inward due to tidal dissipation. This analytic result \Gamma=\Gamma(\gamma,\beta,q,p,\eta,\theta) is essentially exact for initially circular Orbits and holds to within an accuracy of 50% over the entire multi-dimensional parameter space, where the individual parameters vary by several orders of magnitude. For stars that experience mass loss, the stellar radius often displays quasi-periodic variations, which produce corresponding variations in tidal forcing; we generalize the calculation to include such pulsations using a semi-analytic treatment that holds to the same accuracy as the non-pulsating case. These results can be used in many applications, e.g., to predict/constrain properties of Planetary systems orbiting white dwarfs.
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evolution of Planetary Orbits with stellar mass loss and tidal dissipation
The Astrophysical Journal, 2013Co-Authors: Fred C. Adams, Anthony M. BlochAbstract:Intermediate mass stars and stellar remnants often host planets, and these dynamical systems evolve because of mass loss and tides. This paper considers the combined action of stellar mass loss and tidal dissipation on Planetary Orbits in order to determine the conditions required for Planetary survival. Stellar mass loss is included using a so-called Jeans model, described by a dimensionless mass loss rate γ and an index β. We use an analogous prescription to model tidal effects, described here by a dimensionless dissipation rate Γ and two indices (q, p). The initial conditions are determined by the starting value of angular momentum parameter η0 (equivalently, the initial eccentricity) and the phase θ of the orbit. Within the context of this model, we derive an analytic formula for the critical dissipation rate Γ, which marks the boundary between Orbits that spiral outward due to stellar mass loss and those that spiral inward due to tidal dissipation. This analytic result Γ = Γ(γ, β, q, p, η0, θ) is essentially exact for initially circular Orbits and holds to within an accuracy of ≈50% over the entire multi-dimensional parameter space, where the individual parameters vary by several orders of magnitude. For stars that experience mass loss, the stellar radius often displays quasi-periodic variations, which produce corresponding variations in tidal forcing; we generalize the calculation to include such pulsations using a semi-analytic treatment that holds to the same accuracy as the non-pulsating case. These results can be used in many applications, e.g., to predict/constrain properties of Planetary systems orbiting white dwarfs.
Frederic A Rasio - One of the best experts on this subject based on the ideXlab platform.
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tidal decay of close Planetary Orbits
arXiv: Astrophysics, 1996Co-Authors: Frederic A Rasio, Christopher A Tout, S H Lubow, M LivioAbstract:The 4.2-day orbit of the newly discovered planet around 51~Pegasi is formally unstable to tidal dissipation. However, the orbital decay time in this system is longer than the main-sequence lifetime of the central star. Given our best current understanding of tidal interactions, a planet of Jupiter's mass around a solar-like star could have dynamically survived in an orbit with a period as short as $\sim10\,$hr. Since radial velocities increase with decreasing period, we would expect to find those planets close to the tidal limit first and, unless this is a very unusual system, we would expect to find many more. We also consider the tidal stability of planets around more evolved stars and we re-examine in particular the question of whether the Earth can dynamically survive the red-giant phase in the evolution of the Sun.
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tidal decay of close Planetary Orbits
The Astrophysical Journal, 1996Co-Authors: Frederic A Rasio, Christopher A Tout, S H Lubow, M LivioAbstract:The 4.2-day orbit of the newly discovered planet around 51 Pegasi is formally unstable to tidal dissipation. However, the orbital decay time in this system is longer than the main-sequence lifetime of the central star. Given our best current understanding of tidal interactions, a planet of Jupiter’s mass around a solar-like star could have dynamically survived in an orbit with a period as short as ∼ 10 hr. Since radial velocities increase with decreasing period, we would expect to find those planets close to the tidal limit first and, unless this is a very unusual system, we would expect to find many more. We also consider the tidal stability of planets around more evolved stars and we re-examine in particular the question of whether the Earth can dynamically survive the red-giant phase in the evolution of the Sun. Subject headings: Planets and Satellites: General — Solar System: General — Stars: Planetary Systems — Sun: Solar-terrestrial Relations
Zdzislaw E. Musielak - One of the best experts on this subject based on the ideXlab platform.
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Erratum Stability of Planetary Orbits in binary systems
2008Co-Authors: Zdzislaw E. Musielak, Manfred Cuntz, E. A. Marshall, T. D. StuitAbstract:This paper studies the stability of S-type and P-type Planetary Orbits in binary systems. Stability limits are expressed in units of RAG/RAB ,w hereRAG denotes the distance between the primary star and the planet and RAB denotes the distance between the two stars. The presentation about S-type Orbits is correct, but concerning the P-type Orbits (where the planet is orbiting both stars), the RAG/RAB ratios given in the paper are consistently too small by a factor of two, although the computations themselves are correct. This affects Sect. 4.2 of the paper, where Table 5 and Fig. 6 need to be modified (for corrections, see below). Moreover, in the Abstract, the Conclusions, and Sect. 4.3, it should read: for P-type Orbits, the regions of stability also depend on that distance ratio, in the range of 3.50 and 4.90, again depending on the mass ratio.
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Stringent Criteria for Stable and Unstable Planetary Orbits in Stellar Binary Systems
The Astrophysical Journal, 2007Co-Authors: Manfred Cuntz, J. Eberle, Zdzislaw E. MusielakAbstract:The existence of planets in stellar binary (and higher order) systems has now been confirmed by many observations. The stability of Planetary Orbits in these systems has been extensively studied, but no precise stability criteria have so far been introduced. Therefore, there is an urgent need for developing stringent mathematical criteria that allow us to precisely determine whether a Planetary orbit in a binary system is stable or unstable. In this Letter, such criteria are defined using the concept of Jacobi's integral and Jacobi's constant. These criteria are used to contest previous results on Planetary orbital stability in binary systems.
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Stability of Planetary Orbits in binary systems
Astronomy & Astrophysics, 2005Co-Authors: Zdzislaw E. Musielak, Manfred Cuntz, E. A. Marshall, T. D. StuitAbstract:Stability of S-type and P-type Planetary Orbits in binary systems of different mass and separation ratios is inves- tigated. Criteria for stable, marginally stable and unstable Planetary Orbits are specified. These criteria are used to determine regions of stability of Planetary Orbits in different binary systems with Jupiter-type planets. The obtained results show that the regions of stability for S-type Orbits depend on the distance ratio between the star and planet, and the stellar companions, in the range of 0.22 and 0.46, depending on the mass ratio. For P-type Orbits, the regions of stability also depend on that distance ratio, in the range of 1.75 and 2.45, again depending on the the mass ratio. Applications of these results to three observed binary systems with giant planets, namely, τ Boo, HD 195019 and GJ 86, show that the Orbits of the giant planets in those systems can be classified as stable, as expected.
