Some dynamical aspects of the accretion of Uranus and Neptune: The exchange of orbital angular momentum with planetesimals

Fernández, Julio A.; Ip, W.-H.

doi:10.1016/0019-1035(84)90101-5

Cited by 444 publications

(344 citation statements)

References 18 publications

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“…Without the gas, the planetesimal velocity dispersion rapidly increases, cutting off solid accretion except in the case of stochastic, high-velocity collisions (e.g. Fernandez and Ip 1984). Such a collision could be responsible for Uranus' extreme rotation axis tilt.…”

Section: Discussion: Model Strengths and Weaknessesmentioning

confidence: 99%

The formation of Uranus and Neptune in solid-rich feeding zones: Connecting chemistry and dynamics

Dodson-Robinson

Bodenheimer

2010

Icarus

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The core accretion theory of planet formation has at least two fundamental problems explaining the origins of Uranus and Neptune: (1) dynamical times in the trans-Saturnian solar nebula are so long that core growth can take > 15 Myr, and (2) the onset of runaway gas accretion that begins when cores reach ∼ 10M ⊕ necessitates a sudden gas accretion cutoff just as Uranus and Neptune's cores reach critical mass. Both problems may be resolved by allowing the ice giants to migrate outward after their formation in solid-rich feeding zones with planetesimal surface densities well above the minimum-mass solar nebula. We present new simulations of the formation of Uranus and Neptune in the solid-rich disk of using the initial semimajor axis distribution of the Nice model Morbidelli et al. 2005;Tsiganis et al. 2005), with one ice giant forming at 12 AU and the other at 15 AU. The innermost ice giant reaches its present mass after 3.8-4.0 Myr and the outermost after 5.3-6 Myr, a considerable time decrease from previous one-dimensional simulations (e.g. Pollack et al. 1996). The core masses stay subcritical, eliminating the need for a sudden gas accretion cutoff.Our calculated carbon mass fractions of 22% are in excellent agreement with the ice giant interior models of Podolak et al. (1995) and Marley et al. (1995). Based on the requirement that the ice giant-forming planetesimals contain > 10% mass fractions of methane ice, we can reject any solar system formation model that initially places Uranus and Neptune inside of Saturn's orbit. We also demonstrate that a large population of planetesimals must be present in both ice giant feeding zones throughout the lifetime of the gaseous nebula. This research marks a substantial step forward in connecting both the dynamical and chemical aspects of planet formation. Although we cannot say that the solid-rich solar nebula model of gives exactly the appropriate initial conditions for planet formation, rigorous chemical and dynamical tests have at least revealed it to be a viable model of the early solar system.

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Section: Discussion: Model Strengths and Weaknessesmentioning

confidence: 99%

The formation of Uranus and Neptune in solid-rich feeding zones: Connecting chemistry and dynamics

Dodson-Robinson

Bodenheimer

2010

Icarus

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“…It would be worthwhile to measure the extent of eccentricity excitation engendered by the crossings of only high-order resonances, for which the requirements of ring shepherding are less severe. Finally, divergent migration within particle disks (see, e.g, Fernandez & Ip 1984;Murray et al 1998) should also be explored, particularly in light of our finding that divergent resonance crossings are most effective when the ring mass is small compared to the planet mass.…”

Section: Summary and Discussionmentioning

confidence: 99%

Excitation of Orbital Eccentricities by Repeated Resonance Crossings: Requirements

Chiang

2003

ApJ

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Divergent migration of planets within a viscous circumstellar disk can engender resonance crossings and dramatic excitation of orbital eccentricities. We provide quantitative criteria for the viability of this mechanism. For the orbits of two bodies to diverge, a ring of viscous material must be shepherded between them. As the ring diffuses in radius by virtue of its intrinsic viscosity, the two planets are wedged farther apart. The ring mass must be smaller than the planetary masses so that the crossing of an individual resonance lasts longer than the resonant libration period. At the same time, the resonance crossing cannot be of such long duration that the disk's direct influence on the bodies' eccentricities interferes with the resonant interaction between the two planets. This last criterion is robustly satisfied because resonant widths are typically tiny fractions of the orbital radius. We evaluate our criteria not only for giant planets within gaseous protoplanetary disks but also for shepherd moons that bracket narrow planetary rings in the solar system. A shepherded ring of gas orbiting at a distance of 1 AU from a solar-type star and having a surface density of less than 500 g cm À2 , a dimensionless alpha viscosity of 0.1, and a height-to-radius aspect ratio of 0.05 can drive two Jupiter-mass planets through the 2 : 1 and higher order resonances so that their eccentricities amplify to values of several tenths. Because of the requirement that the disk mass in the vicinity of the planets be smaller than the planet masses, divergent resonance crossings may figure significantly into the orbital evolution of planets during the later stages of protoplanetary disk evolution, including the debris disk phase.

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“…Like most models, the Nice model was based on pre-existing ideas. First, it was known since Fernandez and Ip (1984) that, after the disappearance of the gas, while scattering away the primordial planetesimals from their neighboring regions, the giant planets had to migrate in -5 -semi-major axis as a consequence of angular momentum conservation. Given the configuration of the giant planets in our Solar System, this migration should have had a general trend.…”

Section: The Original Modelmentioning

confidence: 99%

A coherent and comprehensive model of the evolution of the outer Solar System

Morbidelli¹

2010

Comptes Rendus. Physique

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Since the discovery of the first extra-solar planets, we are confronted with the puzzling diversity of planetary systems. Processes like planet radial migration in gasdisks and planetary orbital instabilities, often invoked to explain the exotic orbits of the extra-solar planets, at first sight do not seem to have played a role in our system.In reality, though, there are several aspects in the structure of our Solar System that cannot be explained in the classic scenario of in-situ formation and smooth evolution of the giant planets. This paper describes a new view of the evolution of the outer Solar System that emerges from the so-called 'Nice model' and its recent extensions. The story provided by this model describes a very "dynamical" Solar System, with giant planets affected by both radial migrations and a temporary orbital instability. Thus, the diversity between our system and those found so far around other stars does not seem to be due to different processes that operated here and elsewhere, but rather stems from the strong sensitivity of chaotic evolutions to small differences in the initial and environmental conditions.In press in "C.R. Physique de l'Académie des Sciences".

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Some dynamical aspects of the accretion of Uranus and Neptune: The exchange of orbital angular momentum with planetesimals

Cited by 444 publications

References 18 publications

The formation of Uranus and Neptune in solid-rich feeding zones: Connecting chemistry and dynamics

The formation of Uranus and Neptune in solid-rich feeding zones: Connecting chemistry and dynamics

Excitation of Orbital Eccentricities by Repeated Resonance Crossings: Requirements

A coherent and comprehensive model of the evolution of the outer Solar System

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