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Outcomes of Grazing Impacts Between Sub-Neptunes in Kepler Multis
Earth and Planetary Astrophysics · Submitted 6 Jul 2017
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We dynamically integrate the remnant systems, examine the stability, and estimate the final densities, finding the remnant densities are sensitive to the core masses, and collisions result in generally more stable systems.
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The abstract, sentence by sentence
Studies of high-multiplicity, tightly-packed planetary systems suggest that dynamical instabilities are common and affect both the orbits and planet structures, where the compact orbits and typically low densities make physical collisions likely outcomes. Since the structure of many of these planets is such that the mass is dominated by a rocky core, but the volume is dominated by a tenuous gas envelope, the sticky-sphere approximation, used in dynamical integrators, may be a poor model for these collisions. We perform five sets of collision calculations, including detailed hydrodynamics, sampling mass ratios and core mass fractions typical in Kepler Multis. In our primary set of calculations, we use Kepler-36 as a nominal remnant system, as the two planets have a small dynamical separation and an extreme density ratio. We use an N-body code, Mercury 6.2, to integrate initially unstable systems and study the resultant collisions in detail. We use these collisions, focusing on grazing collisions, in combination with realistic planet models created using gas profiles from Modules for Experiments in Stellar Astrophysics and core profiles using equations of state from Seager et al. (2007), to perform hydrodynamic calculations, finding scatterings, mergers, and even a potential planet-planet binary. We dynamically integrate the remnant systems, examine the stability, and estimate the final densities, finding the remnant densities are sensitive to the core masses, and collisions result in generally more stable systems. We provide prescriptions for predicting the outcomes and modeling the changes in mass and orbits following collisions for general use in dynamical integrators.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Studies of high-multiplicity, tightly-packed planetary systems suggest that dynamical instabilities are common and affect both the orbits and planet structures, where the compact orbits and typically low densities make physical collisions likely outcomes. | background 1.00 | 0.05 | 0.06 | hedged possibility 0.94 |
| s1 | Since the structure of many of these planets is such that the mass is dominated by a rocky core, but the volume is dominated by a tenuous gas envelope, the sticky-sphere approximation, used in dynamical integrators, may be a poor model for these collisions. | background 0.50 | 0.07 | 0.05 | hedged possibility 1.00 |
| s2 | We perform five sets of collision calculations, including detailed hydrodynamics, sampling mass ratios and core mass fractions typical in Kepler Multis. | method 0.83 | 0.97 | 0.03 | asserted 0.99 |
| s3 | In our primary set of calculations, we use Kepler-36 as a nominal remnant system, as the two planets have a small dynamical separation and an extreme density ratio. | method 0.96 | 0.65 | 0.03 | asserted 1.00 |
| s4 | We use an N-body code, Mercury 6.2, to integrate initially unstable systems and study the resultant collisions in detail. | method 1.00 | 0.91 | 0.02 | asserted 0.98 |
| s5 | We use these collisions, focusing on grazing collisions, in combination with realistic planet models created using gas profiles from Modules for Experiments in Stellar Astrophysics and core profiles using equations of state from Seager et al. (2007), to perform hydrodynamic calculations, finding scatterings, mergers, and even a potential planet-planet binary. | method 0.91 | 0.97 | 0.14 | asserted 0.94 |
| s6 | We dynamically integrate the remnant systems, examine the stability, and estimate the final densities, finding the remnant densities are sensitive to the core masses, and collisions result in generally more stable systems. | result 0.98 | 0.97 | 0.44 | asserted 1.00 |
| s7 | We provide prescriptions for predicting the outcomes and modeling the changes in mass and orbits following collisions for general use in dynamical integrators. | contribution 0.97 | 0.92 | 0.28 | asserted 0.98 |
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Original abstract
Studies of high-multiplicity, tightly-packed planetary systems suggest that dynamical instabilities are common and affect both the orbits and planet structures, where the compact orbits and typically low densities make physical collisions likely outcomes. Since the structure of many of these planets is such that the mass is dominated by a rocky core, but the volume is dominated by a tenuous gas envelope, the sticky-sphere approximation, used in dynamical integrators, may be a poor model for these collisions. We perform five sets of collision calculations, including detailed hydrodynamics, sampling mass ratios and core mass fractions typical in Kepler Multis. In our primary set of calculations, we use Kepler-36 as a nominal remnant system, as the two planets have a small dynamical separation and an extreme density ratio. We use an N-body code, Mercury 6.2, to integrate initially unstable systems and study the resultant collisions in detail. We use these collisions, focusing on grazing collisions, in combination with realistic planet models created using gas profiles from Modules for Experiments in Stellar Astrophysics and core profiles using equations of state from Seager et al. (2007), to perform hydrodynamic calculations, finding scatterings, mergers, and even a potential planet-planet binary. We dynamically integrate the remnant systems, examine the stability, and estimate the final densities, finding the remnant densities are sensitive to the core masses, and collisions result in generally more stable systems. We provide prescriptions for predicting the outcomes and modeling the changes in mass and orbits following collisions for general use in dynamical integrators.
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How the literature uses it
1 arXiv paper cite this in 1 sentence
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Uses the method or tool of 1 paper
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Following [ref] , we define the inner binary as the two bound planets and the outer binary as the bound planet-pair and the host star, and compare the maximum apoapsis of the inner binary to the mutual Hill radius at the periapsis of the outer binary, [equation] [equation] where $m_2 > m_1$, and $a_in$, $e_in$, $a_out$, and $e_out$ are the semi-major axes and eccentricities of the inner and outer binary.
On the Possibility of Tidal Formation of Binary Planets Around Ordinary Stars · Bound Planet-Pair · 1.00
Cites as background 1 paper
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[ref] discuss the possibility of tidal dissipation of orbital energy leading to potentially stable gas-giant binaries.
On the Possibility of Tidal Formation of Binary Planets Around Ordinary Stars · Introduction · 0.96
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