scholarly journals How planetary growth outperforms migration

2019 ◽  
Vol 622 ◽  
pp. A202 ◽  
Author(s):  
Anders Johansen ◽  
Shigeru Ida ◽  
Ramon Brasser
Keyword(s):  
Flux Ratio ◽  
Stokes Number ◽  
Giant Planets ◽  
Type I ◽  
Initial Size ◽  
Horizontal Migration ◽  
Gas Giant ◽  
Planetary Migration ◽  
Gas Accretion ◽  
Core Accretion

Planetary migration is a major challenge for planet-formation theories. The speed of type-I migration is proportional to the mass of a protoplanet, while the final decade of growth of a pebble-accreting planetary core takes place at a rate that scales with the mass to the two-thirds power. This results in planetary growth tracks (i.e., the evolution of the mass of a protoplanet versus its distance from the star) that become increasingly horizontal (migration dominated) with the rising mass of the protoplanet. It has been shown recently that the migration torque on a protoplanet is reduced proportional to the relative height of the gas gap carved by the growing planet. Here we show from 1D simulations of planet–disc interaction that the mass at which a planet carves a 50% gap is approximately 2.3 times the pebble isolation mass. Our measurements of the pebble isolation mass from 1D simulations match published 3D results relatively well, except at very low viscosities (α < 10−3) where the 3D pebble isolation mass is significantly higher, possibly due to gap edge instabilities that are not captured in 1D. The pebble isolation mass demarks the transition from pebble accretion to gas accretion. Gas accretion to form gas-giant planets therefore takes place over a few astronomical units of migration after reaching first the pebble isolation mass and, shortly after, the 50% gap mass. Our results demonstrate how planetary growth can outperform migration both during core accretion and during gas accretion, even when the Stokes number of the pebbles is small, St ~ 0.01, and the pebble-to-gas flux ratio in the protoplanetary disc is in the nominal range of 0.01–0.02. We find that planetary growth is very rapid in the first million years of the protoplanetary disc and that the probability for forming gas-giant planets increases with the initial size of the protoplanetary disc and with decreasing turbulent diffusion.

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

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.

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

2020 ◽  
Vol 637 ◽  
pp. A11 ◽  
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.

scholarly journals Planetary migration in gaseous protoplanetary disks

2007 ◽  
Vol 3 (S249) ◽  
pp. 331-346
Author(s):  
Frédéric S. Masset
Keyword(s):  
Major Axis ◽  
Giant Planets ◽  
Type I ◽  
Type Ii ◽  
Orbital Elements ◽  
Intermediate Mass ◽  
Semi Major Axis ◽  
Low Mass ◽  
Planetary Migration ◽  
Different Parts

AbstractTides come from the fact that different parts of a system do not fall in exactly the same way in a non-uniform gravity field. In the case of a protoplanetary disk perturbed by an orbiting, prograde protoplanet, the protoplanet tides raise a wake in the disk which causes the orbital elements of the planet to change over time. The most spectacular result of this process is a change in the protoplanet's semi-major axis, which can decrease by orders of magnitude on timescales shorter than the disk lifetime. This drift in the semi-major axis is called planetary migration. In a first part, we describe how the planet and disk exchange angular momentum and energy at the Lindblad and corotation resonances. Next we review the various types of planetary migration that have so far been contemplated: type I migration, which corresponds to low-mass planets (less than a few Earth masses) triggering a linear disk response; type II migration, which corresponds to massive planets (typically at least one Jupiter mass) that open up a gap in the disk; “runaway” or type III migration, which corresponds to sub-giant planets that orbit in massive disks; and stochastic or diffusive migration, which is the migration mode of low- or intermediate-mass planets embedded in turbulent disks. Lastly, we present some recent results in the field of planetary migration.

scholarly journals Promoted mass growth of multiple, distant giant planets through pebble accretion and planet–planet collision

2020 ◽  
Vol 496 (3) ◽  
pp. 3314-3325 ◽  
Author(s):  
John Wimarsson ◽  
Beibei Liu ◽  
Masahiro Ogihara
Keyword(s):  
Radial Velocity ◽  
Giant Planet ◽  
Giant Planets ◽  
Type I ◽  
Type Ii ◽  
Mass Growth ◽  
Slow Type ◽  
Low Mass ◽  
And Migration ◽  
Gas Accretion

ABSTRACT We propose a pebble-driven planet formation scenario to form giant planets with high multiplicity and large orbital distances in the early gas disc phase. We perform N-body simulations to investigate the growth and migration of low-mass protoplanets in the disc with inner viscously heated and outer stellar irradiated regions. The key feature of this model is that the giant planet cores grow rapidly by a combination of pebble accretion and planet–planet collisions. This consequently speeds up their gas accretion. Because of efficient growth, the planet transitions from rapid type I migration to slow type II migration early, reducing the inward migration substantially. Multiple giant planets can sequentially form in this way with increasing semimajor axes. Both mass growth and orbital retention are more pronounced when a large number of protoplanets are taken into account compared to the case of single planet growth. Eventually, a few numbers of giant planets form with orbital distances of a few to a few tens of aus within 1.5–3 Myr after the birth of the protoplanets. The resulting simulated planet populations could be linked to the substructures exhibited in disc observations as well as large orbital distance exoplanets observed in radial velocity and microlensing surveys.

Formation of gas giant planets: core accretion models with fragmentation and planetary envelope

Icarus ◽  
2003 ◽  
Vol 166 (1) ◽  
pp. 46-62 ◽  
Author(s):  
S. Inaba ◽  
G.W. Wetherill ◽  
M. Ikoma
Keyword(s):  
Giant Planets ◽  
Gas Giant ◽  
Core Accretion

scholarly journals Metallicity and Planet Formation: Models

2009 ◽  
Vol 5 (S265) ◽  
pp. 391-398
Author(s):  
Alan P. Boss
Keyword(s):  
Star Formation ◽  
Strong Correlation ◽  
Planet Formation ◽  
Protoplanetary Disks ◽  
Giant Planets ◽  
Heavy Elements ◽  
Doppler Spectroscopy ◽  
Gas Giant ◽  
Core Accretion ◽  
Gaseous Envelopes

AbstractPlanets typically are considerably more metal-rich than even the most metal-rich stars, one indication that planet formation must differ greatly from star formation. There is general agreement that terrestrial planets form by the collisional accumulation of solids composed of heavy elements in the inner regions of protoplanetary disks. Two competing mechanisms exist for the formation of giant planets, core accretion and disk instability, though hybrid combinations are possible as well. In core accretion, a higher metallicity in the protoplanetary disk leads directly to larger core masses and hence to more gas giant planets. Given the strong correlation of gas giant planets detected by Doppler spectroscopy with stellar metallicity, this has often been taken as proof that core accretion is the mechanism that forms giant planets. Recent work, however, implies that the formation of gas giants by disk instability can be enhanced by higher metallicities, though not as dramatically as for core accretion. In both scenarios, the ongoing accretion of planetesimals by gas giant protoplanets leads to strong enrichments of heavy elements in their gaseous envelopes. Both scenarios also imply that gas giant planets should have significant solid cores, raising questions for gas giant interior models without cores. Exoplanets with large inferred core masses seem likely to have formed by core accretion, while gas giants at distances beyond 20 AU seem more likely to have formed by disk instability. Given the wide variety of exoplanets found to date, it appears that both mechanisms are needed to explain the formation of the known population of giant planets.

scholarly journals LIPAD Simulations of Giant Planet Core Formation

2013 ◽  
Vol 8 (S299) ◽  
pp. 171-172
Author(s):  
Henry Ngo ◽  
Martin J. Duncan ◽  
Harold F. Levison
Keyword(s):  
Numerical Simulations ◽  
Giant Planet ◽  
Giant Planets ◽  
Core Formation ◽  
Preliminary Results ◽  
Gas Giant ◽  
Gas Accretion ◽  
Collisional Evolution

AbstractWe present some preliminary results from our investigation of giant planetary core formation using numerical simulations with the Lagrangian Integrator for Planetary Accretion and Dynamics (LIPAD) by Levison et al. (2012). LIPAD couples dynamics with collisional evolution, including fragmentation. We start with a cold planetesimal disk using particles of a few kilometres in size. Our simulations show growth from kilometre-sized planetesimals to several Earth-mass sized embryos (tens of thousands of kilometers) can occur. However, these embryos may not be large enough to start runaway gas accretion necessary to build the envelopes of gas giant planets.

scholarly journals Quasi-static contraction during runaway gas accretion onto giant planets

2019 ◽  
Vol 630 ◽  
pp. A82 ◽  
Author(s):  
M. Lambrechts ◽  
E. Lega ◽  
R. P. Nelson ◽  
A. Crida ◽  
A. Morbidelli
Keyword(s):  
Outer Part ◽  
Giant Planets ◽  
Gas Flows ◽  
Solid Core ◽  
Static Contraction ◽  
Accretion Rates ◽  
Outer Atmosphere ◽  
Hydrodynamical Simulations ◽  
Gas Accretion ◽  
Core Accretion

Gas-giant planets, like Jupiter and Saturn, acquire massive gaseous envelopes during the approximately 3 Myr-long lifetimes of protoplanetary discs. In the core accretion scenario, the formation of a solid core of around ten Earth masses triggers a phase of rapid gas accretion. Previous 3D grid-based hydrodynamical simulations found that runaway gas accretion rates correspond to approximately 10 to 100 Jupiter masses per Myr. Such high accretion rates would result in all planets with larger than ten Earth-mass cores to form Jupiter-like planets, which is in clear contrast to the ice giants in the Solar System and the observed exoplanet population. In this work, we used 3D hydrodynamical simulations, that include radiative transfer, to model the growth of the envelope on planets with different masses. We find that gas flows rapidly through the outer part of the envelope, but this flow does not drive accretion. Instead, gas accretion is the result of quasi-static contraction of the inner envelope, which can be orders of magnitude smaller than the mass flow through the outer atmosphere. For planets smaller than Saturn, we measured moderate gas accretion rates that are below one Jupiter mass per Myr. Higher mass planets, however, accrete up to ten times faster and do not reveal a self-driven mechanism that can halt gas accretion. Therefore, the reason for the final masses of Saturn and Jupiter remains difficult to understand, unless their completion coincided with the dissipation of the solar nebula.

scholarly journals Pebble-isolation mass: Scaling law and implications for the formation of super-Earths and gas giants

2018 ◽  
Vol 612 ◽  
pp. A30 ◽  
Author(s):  
Bertram Bitsch ◽  
Alessandro Morbidelli ◽  
Anders Johansen ◽  
Elena Lega ◽  
Michiel Lambrechts ◽  
...  
Keyword(s):  
Turbulent Viscosity ◽  
Scaling Law ◽  
Stokes Number ◽  
Giant Planets ◽  
Mass Scaling ◽  
The Core ◽  
Pressure Bump ◽  
Hydrodynamical Simulations ◽  
Gas Accretion ◽  
Migration Pathways

The growth of a planetary core by pebble accretion stops at the so-called pebble isolation mass, when the core generates a pressure bump that traps drifting pebbles outside its orbit. The value of the pebble isolation mass is crucial in determining the final planet mass. If the isolation mass is very low, gas accretion is protracted and the planet remains at a few Earth masses with a mainly solid composition. For higher values of the pebble isolation mass, the planet might be able to accrete gas from the protoplanetary disc and grow into a gas giant. Previous works have determined a scaling of the pebble isolation mass with cube of the disc aspect ratio. Here, we expand on previous measurements and explore the dependency of the pebble isolation mass on all relevant parameters of the protoplanetary disc. We use 3D hydrodynamical simulations to measure the pebble isolation mass and derive a simple scaling law that captures the dependence on the local disc structure and the turbulent viscosity parameter α. We find that small pebbles, coupled to the gas, with Stokes number τf < 0.005 can drift through the partial gap at pebble isolation mass. However, as the planetary mass increases, particles must be decreasingly smaller to penetrate the pressure bump. Turbulent diffusion of particles, however, can lead to an increase of the pebble isolation mass by a factor of two, depending on the strength of the background viscosity and on the pebble size. We finally explore the implications of the new scaling law of the pebble isolation mass on the formation of planetary systems by numerically integrating the growth and migration pathways of planets in evolving protoplanetary discs. Compared to models neglecting the dependence of the pebble isolation mass on the α-viscosity, our models including this effect result in higher core masses for giant planets. These higher core masses are more similar to the core masses of the giant planets in the solar system.

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