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Reem Sari - One of the best experts on this subject based on the ideXlab platform.
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equilibrium configurations of synchronous binaries numerical solutions and application to kuiper belt binary 2001 qg298
The Astrophysical Journal, 2010Co-Authors: Orly Gnat, Reem SariAbstract:We present numerical computations of the equilibrium configurations of tidally locked homogeneous binaries rotating in circular orbits. Unlike the classical Roche approximations, we self-consistently account for the tidal and rotational deformations of both components, and relax the assumptions of ellipsoidal configurations and Keplerian rotation. We find numerical solutions for mass ratios q between 10^(–3) and 1, starting at a small angular velocity for which tidal and rotational deformations are small, and following a sequence of increasing angular velocities. Each series terminates at an appropriate "Roche Limit," above which no equilibrium solution can be found. Even though the Roche Limit is crossed before the "Roche lobe" is filled, any further increase in the angular velocity will result in mass-loss. For close, comparable-mass binaries, we find that local deviations from ellipsoidal forms may be as large as 10%-20%, and departures from Keplerian rotation are significant. We compute the light curves that arise from our equilibrium configurations, assuming their distance is ≫1 AU (e.g., in the Kuiper Belt). We consider both backscatter (proportional to the projected area) and diffuse (Lambert) reflections. Backscatter reflection always yields two minima of equal depths. Diffuse reflection, which is sensitive to the surface curvature, generally gives rise to unequal minima. We find detectable intensity differences of up to 10% between our light curves and those arising from the Roche approximations. Finally, we apply our models to Kuiper Belt binary 2001 QG298, and find a nearly edge-on binary with a mass ratio q = 0.93^(+0.07)_(–0.03), angular velocity ω^2/Gρ = 0.333 ± 0.001 (statistical errors only), and pure diffuse reflection. For the observed period of 2001 QG_(298), these parameters imply a bulk density ρ = 0.72 ± 0.04 g cm^(–3).
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equilibrium configurations of synchronous binaries numerical solutions and application to kuiper belt binary 2001 qg298
arXiv: Earth and Planetary Astrophysics, 2010Co-Authors: Orly Gnat, Reem SariAbstract:We present numerical computations of the equilibrium configurations of tidally-locked homogeneous binaries, rotating in circular orbits. Unlike the classical Roche approximations, we self-consistently account for the tidal and rotational deformations of both components, and relax the assumptions of ellipsoidal configurations and Keplerian rotation. We find numerical solutions for mass ratios q between 1e-3 and 1, starting at a small angular velocity for which tidal and rotational deformations are small, and following a sequence of increasing angular velocities. Each series terminates at an appropriate ``Roche Limit'', above which no equilibrium solution can be found. Even though the Roche Limit is crossed before the ``Roche lobe'' is filled, any further increase in the angular velocity will result in mass-loss. For close, comparable-mass binaries, we find that local deviations from ellipsoidal forms may be as large as 10-20%, and departures from Keplerian rotation are significant. We compute the light curves that arise from our equilibrium configurations, assuming their distance is >>1 AU (e.g. in the Kuiper Belt). We consider both backscatter (proportional to the projected area) and diffuse (Lambert) reflections. Backscatter reflection always yields two minima of equal depths. Diffuse reflection, which is sensitive to the surface curvature, generally gives rise to unequal minima. We find detectable intensity differences of up to 10% between our light curves and those arising from the Roche approximations. Finally, we apply our models to Kuiper Belt binary 2001 QG298, and find a nearly edge-on binary with a mass ratio q = 0.93 ^{+0.07}_{-0.03}, angular velocity Omega^2/G rho = 0.333+/-0.001 (statistical errors only), and pure diffuse reflection. For the observed period of 2001 QG298, these parameters imply a bulk density, rho = 0.72 +/- 0.04 g cm^-3.
Julien Salmon - One of the best experts on this subject based on the ideXlab platform.
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accretion of saturn s inner mid sized moons from a massive primordial ice ring
The Astrophysical Journal, 2017Co-Authors: Julien Salmon, R M CanupAbstract:Saturn's rings are rock-poor, containing 90 to 95% ice by mass. As a group, Saturn's moons interior to and including Tethys are also about 90% ice. Tethys itself contains 40% rock. Here we simulate the evolution of a massive primordial ice-rich ring and the production of satellites as ring material spreads beyond the Roche Limit. We describe the Roche-interior ring with an analytic model, and use an N-body code to describe material beyond the Roche Limit. We track the accretion and interactions of spawned satellites, including tidal interaction with the planet, assuming a tidal dissipation factor for Saturn of Q ~ 104. We find that ring torques and capture of moons into mutual resonances produces a system of ice-rich inner moons that extends outward to approximately Tethys's orbit in 109 years, even with relatively slow orbital expansion due to tides. The resulting mass and semi-major axis distribution of spawned moons resembles that of Mimas, Enceladus and Tethys. We estimate the mass of rock delivered to the moons by external cometary impactors during a late-heavy bombardment. We find that the inner moons receive a mass in rock comparable to their current total rock content, while Dione and Rhea receive an order-of-magnitude less rock than their current rock content. This suggests that external contamination may have been the primary source of rock in the inner moons, and that Dione and Rhea formed from much more rock-rich source material. Reproducing the distribution of rock among the current inner moons is challenging, and appears to require large impactors and stochasticity and/or the presence of some rock in the initial ring.
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Lunar accretion from a Roche-interior fluid disk
Astrophysical Journal, 2012Co-Authors: Julien Salmon, R M CanupAbstract:We use a hybrid numerical approach to simulate the formation of the Moon from an impact-generated disk, consisting of a fluid model for the disk inside the Roche Limit and an N-body code to describe accretion outside the Roche Limit. As the inner disk spreads due to a thermally regulated viscosity, material is delivered across the Roche Limit and accretes into moonlets that are added to the N-body simulation. Contrary to an accretion timescale of a few months obtained with prior pure N-body codes, here the final stage of the Moon's growth is controlled by the slow spreading of the inner disk, resulting in a total lunar accretion timescale of ~10^2 years. It has been proposed that the inner disk may compositionally equilibrate with the Earth through diffusive mixing, which offers a potential explanation for the identical oxygen isotope compositions of the Earth and Moon. However, the mass fraction of the final Moon that is derived from the inner disk is Limited by resonant torques between the disk and exterior growing moons. For initial disks containing < 2.5 lunar masses (ML), we find that a final Moon with mass > 0.8ML contains < 60% material derived from the inner disk, with this material preferentially delivered to the Moon at the end of its accretion.
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lunar accretion from a Roche interior fluid disk
epsc, 2012Co-Authors: Julien Salmon, R M CanupAbstract:We use a hybrid numerical approach to simulate the formation of the Moon from an impact-generated disk, consisting of a fluid model for the disk inside the Roche Limit and an N-body code to describe accretion outside the Roche Limit. As the inner disk spreads due to a thermally regulated viscosity, material is delivered across the Roche Limit and accretes into moonlets that are added to the N-body simulation. Contrary to an accretion timescale of a few months obtained with prior pure N-body codes, here the final stage of the Moon’s growth is controlled by the slow spreading of the inner disk, resulting in a total lunar accretion timescale of ∼ 10 2 years. It has been proposed that the inner disk may compositionally equilibrate with the Earth through diffusive mixing, which offers a potential explanation for the identical oxygen isotope compositions of the Earth and Moon. However, the mass fraction of the final Moon that is derived from the inner disk is Limited by resonant torques between the disk and exterior growing moons. For initial disks containing 0.8MK contains ≤ 60% material derived from the inner disk, with this material preferentially delivered to the Moon at the end of its accretion.
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long term and large scale viscous evolution of dense planetary rings
Icarus, 2010Co-Authors: Julien Salmon, Sebastien Charnoz, Aurelien Crida, A BrahicAbstract:Abstract Planetary rings are common in the outer Solar System but their origin and long-term evolution is still a matter of debate. It is well known that viscous spreading is a major evolutionary process for rings, as it globally redistributes the disk’s mass and angular momentum, and can lead to the disk’s loosing mass by infall onto the planet or through the Roche Limit. However, describing this process is highly dependent on the model used for the viscosity. In this paper we investigate the global and long-term viscous evolution of a circumplanetary disk. We have developed a simple 1D numerical code, but we use a physically realistic viscosity model derived from N-body simulations ( Daisaka et al., 2001 ), and dependent on the disk’s local properties (surface mass density, particle size, distance to the planet). Particularly, we include the effects of gravitational instabilities (wakes) that importantly enhance the disk’s viscosity. This method allows to study the global evolution of the disk over the age of the Solar System. Common estimates of the disk’s spreading time-scales with constant viscosity significantly underestimate the rings’ lifetime. We show that, with a realistic viscosity model, an initially narrow ring undergoes two successive evolutionary stages: (1) a transient rapid spreading when the disk is self-gravitating, with the formation of a density peak inward and an outer region marginally gravitationally stable, and with an emptying time-scale proportional to 1 / M 0 2 (where M0 is the disk’s initial mass), (2) an asymptotic regime where the spreading rate continuously slows down as larger parts of the disk become non-self-gravitating due to the decrease of the surface density, until the disk becomes completely non-self-gravitating. At this point its evolution dramatically slows down, with an emptying time-scale proportional to 1/M0, which significantly increases the disk’s lifetime compared to the case with constant viscosity. We show also that the disk’s width scales like t1/4 with the realistic viscosity model, while it scales like t1/2 in the case of constant viscosity, resulting in much larger evolutionary time-scales in our model. We find however that the present shape of Saturn’s rings looks like a 100 million-years old disk in our simulations. Concerning Jupiter’s, Uranus’ and Neptune’s rings that are faint today, it is not likely that they were much more massive in the past and lost most of their mass due to viscous spreading alone.
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the recent formation of saturn s moonlets from viscous spreading of the main rings
Nature, 2010Co-Authors: Sebastien Charnoz, Julien Salmon, Aurelien CridaAbstract:The regular satellites of the giant planets are believed to have finished their accretion concurrent with the planets, about 4.5 Gyr ago. A population of Saturn's small moons orbiting just outside the main rings are dynamically young (less than 10(7) yr old), which is inconsistent with the formation timescale for the regular satellites. They are also underdense ( approximately 600 kg m(-3)) and show spectral characteristics similar to those of the main rings. It has been suggested that they accreted at the rings' edge, but hitherto it has been impossible to model the formation process fully owing to a lack of computational power. Here we report a hybrid simulation in which the viscous spreading of Saturn's rings beyond the Roche Limit (the distance beyond which the rings are gravitationally unstable) gives rise to the small moons. The moonlets' mass distribution and orbital architecture are reproduced. The current confinement of the main rings and the existence of the dusty F ring are shown to be direct consequences of the coupling of viscous evolution and satellite formation. Saturn's rings, like a mini protoplanetary disk, may be the last place where accretion was recently active in the Solar System, some 10(6)-10(7) yr ago.
R M Canup - One of the best experts on this subject based on the ideXlab platform.
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accretion of saturn s inner mid sized moons from a massive primordial ice ring
The Astrophysical Journal, 2017Co-Authors: Julien Salmon, R M CanupAbstract:Saturn's rings are rock-poor, containing 90 to 95% ice by mass. As a group, Saturn's moons interior to and including Tethys are also about 90% ice. Tethys itself contains 40% rock. Here we simulate the evolution of a massive primordial ice-rich ring and the production of satellites as ring material spreads beyond the Roche Limit. We describe the Roche-interior ring with an analytic model, and use an N-body code to describe material beyond the Roche Limit. We track the accretion and interactions of spawned satellites, including tidal interaction with the planet, assuming a tidal dissipation factor for Saturn of Q ~ 104. We find that ring torques and capture of moons into mutual resonances produces a system of ice-rich inner moons that extends outward to approximately Tethys's orbit in 109 years, even with relatively slow orbital expansion due to tides. The resulting mass and semi-major axis distribution of spawned moons resembles that of Mimas, Enceladus and Tethys. We estimate the mass of rock delivered to the moons by external cometary impactors during a late-heavy bombardment. We find that the inner moons receive a mass in rock comparable to their current total rock content, while Dione and Rhea receive an order-of-magnitude less rock than their current rock content. This suggests that external contamination may have been the primary source of rock in the inner moons, and that Dione and Rhea formed from much more rock-rich source material. Reproducing the distribution of rock among the current inner moons is challenging, and appears to require large impactors and stochasticity and/or the presence of some rock in the initial ring.
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Lunar accretion from a Roche-interior fluid disk
Astrophysical Journal, 2012Co-Authors: Julien Salmon, R M CanupAbstract:We use a hybrid numerical approach to simulate the formation of the Moon from an impact-generated disk, consisting of a fluid model for the disk inside the Roche Limit and an N-body code to describe accretion outside the Roche Limit. As the inner disk spreads due to a thermally regulated viscosity, material is delivered across the Roche Limit and accretes into moonlets that are added to the N-body simulation. Contrary to an accretion timescale of a few months obtained with prior pure N-body codes, here the final stage of the Moon's growth is controlled by the slow spreading of the inner disk, resulting in a total lunar accretion timescale of ~10^2 years. It has been proposed that the inner disk may compositionally equilibrate with the Earth through diffusive mixing, which offers a potential explanation for the identical oxygen isotope compositions of the Earth and Moon. However, the mass fraction of the final Moon that is derived from the inner disk is Limited by resonant torques between the disk and exterior growing moons. For initial disks containing < 2.5 lunar masses (ML), we find that a final Moon with mass > 0.8ML contains < 60% material derived from the inner disk, with this material preferentially delivered to the Moon at the end of its accretion.
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lunar accretion from a Roche interior fluid disk
epsc, 2012Co-Authors: Julien Salmon, R M CanupAbstract:We use a hybrid numerical approach to simulate the formation of the Moon from an impact-generated disk, consisting of a fluid model for the disk inside the Roche Limit and an N-body code to describe accretion outside the Roche Limit. As the inner disk spreads due to a thermally regulated viscosity, material is delivered across the Roche Limit and accretes into moonlets that are added to the N-body simulation. Contrary to an accretion timescale of a few months obtained with prior pure N-body codes, here the final stage of the Moon’s growth is controlled by the slow spreading of the inner disk, resulting in a total lunar accretion timescale of ∼ 10 2 years. It has been proposed that the inner disk may compositionally equilibrate with the Earth through diffusive mixing, which offers a potential explanation for the identical oxygen isotope compositions of the Earth and Moon. However, the mass fraction of the final Moon that is derived from the inner disk is Limited by resonant torques between the disk and exterior growing moons. For initial disks containing 0.8MK contains ≤ 60% material derived from the inner disk, with this material preferentially delivered to the Moon at the end of its accretion.
Joshua N Winn - One of the best experts on this subject based on the ideXlab platform.
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the Roche Limit for close orbiting planets minimum density composition constraints and application to the 4 2 hr planet koi 1843 03
The Astrophysical Journal, 2013Co-Authors: S Rappaport, Roberto Sanchisojeda, Leslie A Rogers, Alan M Levine, Joshua N WinnAbstract:The requirement that a planet must orbit outside of its Roche Limit gives a lower Limit on the planet's mean density. The minimum density depends almost entirely on the orbital period and is immune to systematic errors in the stellar properties. We consider the implications of this density constraint for the newly identified class of small planets with periods shorter than half a day. When the planet's radius is accurately known, this lower Limit to the density can be used to restrict the possible combinations of iron and rock within the planet. Applied to KOI 1843.03, a 0.6 R⊕ planet with the shortest known orbital period of 4.245 hr, the planet's mean density must be ≳7 g cm^(–3). By modeling the planetary interior subject to this constraint, we find that the composition of the planet must be mostly iron, with at most a modest fraction of silicates (≾30% by mass).
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the Roche Limit for close orbiting planets minimum density composition constraints and application to the 4 2 hour planet koi 1843 03
arXiv: Earth and Planetary Astrophysics, 2013Co-Authors: S Rappaport, Roberto Sanchisojeda, Leslie A Rogers, Alan M Levine, Joshua N WinnAbstract:The requirement that a planet must orbit outside of its Roche Limit gives a lower Limit on the planet's mean density. The minimum density depends almost entirely on the orbital period and is immune to systematic errors in the stellar properties. We consider the implications of this density constraint for the newly-identified class of small planets with periods shorter than half a day. When the planet's radius is known accurately, this lower Limit to the density can be used to restrict the possible combinations of iron and rock within the planet. Applied to KOI 1843.03, with a radius of 0.6 Earth radii and the shortest known orbital period of 4.245 hr, the planet's mean density must be greater than approximately 7 g/cm^3. By modeling the planetary interior subject to this constraint, we find the composition of the planet must be mostly iron, with at most a modest fraction of silicates (less than approximately 30% by mass).
Orly Gnat - One of the best experts on this subject based on the ideXlab platform.
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equilibrium configurations of synchronous binaries numerical solutions and application to kuiper belt binary 2001 qg298
The Astrophysical Journal, 2010Co-Authors: Orly Gnat, Reem SariAbstract:We present numerical computations of the equilibrium configurations of tidally locked homogeneous binaries rotating in circular orbits. Unlike the classical Roche approximations, we self-consistently account for the tidal and rotational deformations of both components, and relax the assumptions of ellipsoidal configurations and Keplerian rotation. We find numerical solutions for mass ratios q between 10^(–3) and 1, starting at a small angular velocity for which tidal and rotational deformations are small, and following a sequence of increasing angular velocities. Each series terminates at an appropriate "Roche Limit," above which no equilibrium solution can be found. Even though the Roche Limit is crossed before the "Roche lobe" is filled, any further increase in the angular velocity will result in mass-loss. For close, comparable-mass binaries, we find that local deviations from ellipsoidal forms may be as large as 10%-20%, and departures from Keplerian rotation are significant. We compute the light curves that arise from our equilibrium configurations, assuming their distance is ≫1 AU (e.g., in the Kuiper Belt). We consider both backscatter (proportional to the projected area) and diffuse (Lambert) reflections. Backscatter reflection always yields two minima of equal depths. Diffuse reflection, which is sensitive to the surface curvature, generally gives rise to unequal minima. We find detectable intensity differences of up to 10% between our light curves and those arising from the Roche approximations. Finally, we apply our models to Kuiper Belt binary 2001 QG298, and find a nearly edge-on binary with a mass ratio q = 0.93^(+0.07)_(–0.03), angular velocity ω^2/Gρ = 0.333 ± 0.001 (statistical errors only), and pure diffuse reflection. For the observed period of 2001 QG_(298), these parameters imply a bulk density ρ = 0.72 ± 0.04 g cm^(–3).
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equilibrium configurations of synchronous binaries numerical solutions and application to kuiper belt binary 2001 qg298
arXiv: Earth and Planetary Astrophysics, 2010Co-Authors: Orly Gnat, Reem SariAbstract:We present numerical computations of the equilibrium configurations of tidally-locked homogeneous binaries, rotating in circular orbits. Unlike the classical Roche approximations, we self-consistently account for the tidal and rotational deformations of both components, and relax the assumptions of ellipsoidal configurations and Keplerian rotation. We find numerical solutions for mass ratios q between 1e-3 and 1, starting at a small angular velocity for which tidal and rotational deformations are small, and following a sequence of increasing angular velocities. Each series terminates at an appropriate ``Roche Limit'', above which no equilibrium solution can be found. Even though the Roche Limit is crossed before the ``Roche lobe'' is filled, any further increase in the angular velocity will result in mass-loss. For close, comparable-mass binaries, we find that local deviations from ellipsoidal forms may be as large as 10-20%, and departures from Keplerian rotation are significant. We compute the light curves that arise from our equilibrium configurations, assuming their distance is >>1 AU (e.g. in the Kuiper Belt). We consider both backscatter (proportional to the projected area) and diffuse (Lambert) reflections. Backscatter reflection always yields two minima of equal depths. Diffuse reflection, which is sensitive to the surface curvature, generally gives rise to unequal minima. We find detectable intensity differences of up to 10% between our light curves and those arising from the Roche approximations. Finally, we apply our models to Kuiper Belt binary 2001 QG298, and find a nearly edge-on binary with a mass ratio q = 0.93 ^{+0.07}_{-0.03}, angular velocity Omega^2/G rho = 0.333+/-0.001 (statistical errors only), and pure diffuse reflection. For the observed period of 2001 QG298, these parameters imply a bulk density, rho = 0.72 +/- 0.04 g cm^-3.
