Planetary Migration | ScienceGate

AbstractWe investigate the angular momentum distribution of known exoplanetary systems, as a function of the planetary mass, orbital semimajor axis and metallicity of the host star. We find exoplanets seems to be classified according to at least two ‘populations’, with respect to their angular momentum properties. This classification is independent on the composition of the planet and seems to be valid for both jovian and neptunian planets, and probably can be extrapolated to the terrestrial planets of the Solar System. We analyse these ‘populations’ considering the phenomenon of planetary migration.

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Rapid Formation of Gas-giant Planets via Collisional Coagulation from Dust Grains to Planetary Cores

The Astrophysical Journal ◽

10.3847/1538-4357/ac289c ◽

2021 ◽

Vol 922 (1) ◽

pp. 16

Author(s):

Hiroshi Kobayashi ◽

Hidekazu Tanaka

Keyword(s):

Protoplanetary Disks ◽

Central Star ◽

Giant Planets ◽

Solar Systems ◽

Evolution Path ◽

Planetary Cores ◽

Rapid Formation ◽

Gas Giant ◽

Planetary Migration ◽

Gas Accretion

Abstract Gas-giant planets, such as Jupiter, Saturn, and massive exoplanets, were formed via the gas accretion onto the solid cores, each with a mass of roughly 10 Earth masses. However, rapid radial migration due to disk–planet interaction prevents the formation of such massive cores via planetesimal accretion. Comparably rapid core growth via pebble accretion requires very massive protoplanetary disks because most pebbles fall into the central star. Although planetesimal formation, planetary migration, and gas-giant core formation have been studied with a lot of effort, the full evolution path from dust to planets is still uncertain. Here we report the result of full simulations for collisional evolution from dust to planets in a whole disk. Dust growth with realistic porosity allows the formation of icy planetesimals in the inner disk (≲10 au), while pebbles formed in the outer disk drift to the inner disk and there grow to planetesimals. The growth of those pebbles to planetesimals suppresses their radial drift and supplies small planetesimals sustainably in the vicinity of cores. This enables rapid formation of sufficiently massive planetary cores within 0.2–0.4 million years, prior to the planetary migration. Our models shows the first gas giants form at 2–7 au in rather common protoplanetary disks, in agreement with the exoplanet and solar systems.

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RESONANT REMOVAL OF EXOMOONS DURING PLANETARY MIGRATION

The Astrophysical Journal ◽

10.3847/0004-637x/817/1/18 ◽

2016 ◽

Vol 817 (1) ◽

pp. 18 ◽

Cited By ~ 28

Author(s):

Christopher Spalding ◽

Konstantin Batygin ◽

Fred C. Adams

Keyword(s):

Planetary Migration

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Migration of Low-Mass Planets

Oxford Research Encyclopedia of Planetary Science ◽

10.1093/acrefore/9780190647926.013.192 ◽

2021 ◽

Author(s):

Frédéric S. Masset

Keyword(s):

Aerodynamic Drag ◽

Semimajor Axis ◽

Planetary Systems ◽

High Mass ◽

Reverse Migration ◽

Low Viscosity ◽

Kepler Mission ◽

Sensitive Dependence ◽

Low Mass ◽

Planetary Migration

Planet migration is the variation over time of a planet’s semimajor axis, leading to either a contraction or an expansion of the orbit. It results from the exchange of energy and angular momentum between the planet and the disk in which it is embedded during its formation and can cause the semimajor axis to change by as much as two orders of magnitude over the disk’s lifetime. The migration of forming protoplanets is an unavoidable process, and it is thought to be a key ingredient for understanding the variety of extrasolar planetary systems. Although migration occurs for protoplanets of all masses, its properties for low-mass planets (those having up to a few Earth masses) differ significantly from those for high-mass planets. The torque that is exerted by the disk on the planet is composed of different contributions. While migration was first thought to be invariably inward, physical processes that are able to halt or even reverse migration were later uncovered, leading to the realization that the migration path of a forming planet has a very sensitive dependence on the underlying disk parameters. There are other processes that go beyond the case of a single planet experiencing smooth migration under the disk’s tide. This is the case of planetary migration in low-viscosity disks, a fashionable research avenue because protoplanetary disks are thought to have very low viscosity, if any, over most of their planet-forming regions. Such a process is generally significantly chaotic and has to be tackled through high-resolution numerical simulations. The migration of several low-mass planets is also is a very fashionable topic, owing to the discovery by the Kepler mission of many multiple extrasolar planetary systems. The orbital properties of these systems suggest that at least some of them have experienced substantial migration. Although there have been many studies to account for the orbital properties of these systems, there is as yet no clear picture of the different processes that shaped them. Finally, some recently unveiled processes could be important for the migration of low-mass planets. One process is aero-resonant migration, in which a swarm of planetesimals subjected to aerodynamic drag push a planet inward when they reach a mean-motion resonance with the planet, while another process is based on so-called thermal torques, which arise when thermal diffusion in the disk is taken into account, or when the planet, heated by accretion, releases heat into the ambient gas.

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Ploonets: formation, evolution, and detectability of tidally detached exomoons

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2110 ◽

2019 ◽

Vol 489 (2) ◽

pp. 2313-2322 ◽

Cited By ~ 6

Author(s):

Mario Sucerquia ◽

Jaime A Alvarado-Montes ◽

Jorge I Zuluaga ◽

Nicolás Cuello ◽

Cristian Giuppone

Keyword(s):

Planetary System ◽

Orbital Evolution ◽

Giant Planets ◽

Light Curves ◽

Significant Evidence ◽

Object A ◽

Tidal Interactions ◽

Stellar Radiation ◽

Planetary Migration ◽

Intense Research

Abstract Close-in giant planets represent the most significant evidence of planetary migration. If large exomoons form around migrating giant planets which are more stable (e.g. those in the Solar system), what happens to these moons after migration is still under intense research. This paper explores the scenario where large regular exomoons escape after tidal interchange of angular momentum with its parent planet, becoming small planets by themselves. We name this hypothetical type of object a ploonet. By performing semi-analytical simulations of tidal interactions between a large moon with a close-in giant, and integrating numerically their orbits for several Myr, we found that in ∼50 per cent of the cases a young ploonet may survive ejection from the planetary system, or collision with its parent planet and host star, being in principle detectable. Volatile-rich ploonets are dramatically affected by stellar radiation during both planetocentric and siderocentric orbital evolution, and their radius and mass change significantly due to the sublimation of most of their material during time-scales of hundreds of Myr. We estimate the photometric signatures that ploonets may produce if they transit the star during the phase of evaporation, and compare them with noisy light curves of known objects (Kronian stars and non-periodical dips in dusty light curves). Additionally, the typical transit timing variations (TTV) induced by the interaction of a ploonet with its planet are computed. We find that present and future photometric surveys’ capabilities can detect these effects and distinguish them from those produced by other nearby planetary encounters.

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Influence of migration models and thermal torque on planetary growth in the pebble accretion scenario

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037579 ◽

2020 ◽

Vol 637 ◽

pp. A11 ◽

Cited By ~ 3

Author(s):

Thomas Baumann ◽

Bertram Bitsch

Keyword(s):

Planet Formation ◽

Major Axis ◽

Type I ◽

Semi Major Axis ◽

Disk Structure ◽

Accretion Rates ◽

Low Mass ◽

Planetary Migration ◽

Gas Accretion ◽

Outward Migration

Low-mass planets that are in the process of growing larger within protoplanetary disks exchange torques with the disk and change their semi-major axis accordingly. This process is called type I migration and is strongly dependent on the underlying disk structure. As a result, there are many uncertainties about planetary migration in general. In a number of simulations, the current type I migration rates lead to planets reaching the inner edge of the disk within the disk lifetime. A new kind of torque exchange between planet and disk, the thermal torque, aims to slow down inward migration via the heating torque. The heating torque may even cause planets to migrate outwards, if the planetary luminosity is large enough. Here, we study the influence on planetary migration of the thermal torque on top of previous type I models. We find that the formula of Paardekooper et al. (2011, MNRAS, 410, 293) allows for more outward migration than that of Jiménez & Masset (2017, MNRAS, 471, 4917) in most configurations, but we also find that planets evolve to very similar mass and final orbital radius using both formulae in a single planet-formation scenario, including pebble and gas accretion. Adding the thermal torque can introduce new, but small, regions of outwards migration if the accretion rates onto the planet correspond to typical solid accretion rates following the pebble accretion scenario. If the accretion rates onto the planets become very large, as could be the case in environments with large pebble fluxes (e.g., high-metallicity environments), the thermal torque can allow more efficient outward migration. However, even then, the changes for the final mass and orbital positions in our planet formation scenario are quite small. This implies that for single planet evolution scenarios, the influence of the heating torque is probably negligible.

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