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

Bitsch, Bertram LU ; Morbidelli, Alessandro ; Johansen, Anders LU ; Lega, Elena ; Lambrechts, Michiel LU and Crida, Aurélien (2018) In Astronomy and Astrophysics 612.
Abstract


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... (More)


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 τ
f
< 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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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Accretion, Accretion discs, Planet-disc interactions, Planets and satellites: formation, Protoplanetary discs
in
Astronomy and Astrophysics
volume
612
article number
201731931
publisher
EDP Sciences
external identifiers
  • scopus:85063597390
ISSN
0004-6361
DOI
10.1051/0004-6361/201731931
language
English
LU publication?
yes
id
b27babf2-248d-441e-8036-5f4a7ea3f65a
date added to LUP
2019-04-11 11:24:36
date last changed
2024-04-16 03:02:58
@article{b27babf2-248d-441e-8036-5f4a7ea3f65a,
  abstract     = {{<p><br>
                                                         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 τ                             <br>
                            <sub>f</sub><br>
                                                          &lt; 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.                         <br>
                        </p>}},
  author       = {{Bitsch, Bertram and Morbidelli, Alessandro and Johansen, Anders and Lega, Elena and Lambrechts, Michiel and Crida, Aurélien}},
  issn         = {{0004-6361}},
  keywords     = {{Accretion; Accretion discs; Planet-disc interactions; Planets and satellites: formation; Protoplanetary discs}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Pebble-isolation mass : Scaling law and implications for the formation of super-Earths and gas giants}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/201731931}},
  doi          = {{10.1051/0004-6361/201731931}},
  volume       = {{612}},
  year         = {{2018}},
}