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Embryos grown in the dead zone: Assembling the first protoplanetary cores in low mass self-gravitating circumstellar disks of gas and solids
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
2008 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 491, no 3, L41-L44 p.Article in journal (Refereed) Published
Abstract [en]

Context: In the borders of the dead zones of protoplanetary disks, the inflow of gas produces a local density maximum that triggers the Rossby wave instability. The vortices that form are efficient in trapping solids. Aims: We aim to assess the possibility of gravitational collapse of the solids within the Rossby vortices. Methods: We perform global simulations of the dynamics of gas and solids in a low mass non-magnetized self-gravitating thin protoplanetary disk with the Pencil Code. We use multiple particle species of radius 1, 10, 30, and 100 cm. The dead zone is modelled as a region of low viscosity. Results: The Rossby vortices excited in the edges of the dead zone are efficient particle traps. Within 5 orbits after their appearance, the solids achieve critical density and undergo gravitational collapse into Mars sized objects. The velocity dispersions are of the order of 10 m s-1 for newly formed embryos, later lowering to less than 1 m s-1 by drag force cooling. After 200 orbits, over 300 gravitationally bound embryos were formed, 20 of them being more massive than Mars. Their mass spectrum follows a power law of index -2.3 ± 0.2.

Place, publisher, year, edition, pages
2008. Vol. 491, no 3, L41-L44 p.
Keyword [en]
Accretion, accretion disks; Instabilites; Stars: planetary systems: formation
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-98000DOI: 10.1051/0004-6361:200810626ISI: 000261152900001OAI: oai:DiVA.org:uu-98000DiVA: diva2:173151
Available from: 2009-02-05 Created: 2009-02-05 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Turbulence-Assisted Planetary Growth: Hydrodynamical Simulations of Accretion Disks and Planet Formation
Open this publication in new window or tab >>Turbulence-Assisted Planetary Growth: Hydrodynamical Simulations of Accretion Disks and Planet Formation
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The current paradigm in planet formation theory is developed around a hierarquical growth of solid bodies, from interstellar dust grains to rocky planetary cores. A particularly difficult phase in the process is the growth from meter-size boulders to planetary embryos of the size of our Moon or Mars. Objects of this size are expected to drift extremely rapid in a protoplanetary disk, so that they would generally fall into the central star well before larger bodies can form.

In this thesis, we used numerical simulations to find a physical mechanism that may retain solids in some parts of protoplanetary disks long enough to allow for the formation of planetary embryos. We found that such accumulation can happen at the borders of so-called dead zones. These dead zones would be regions where the coupling to the ambient magnetic field is weaker and the turbulence is less strong, or maybe even absent in some cases. We show by hydrodynamical simulations that material accumulating between the turbulent active and dead regions would be trapped into vortices to effectively form planetary embryos of Moon to Mars mass.

We also show that in disks that already formed a giant planet, solid matter accumulates on the edges of the gap the planet carves, as well as at the stable Lagrangian points. The concentration is strong enough for the solids to clump together and form smaller, rocky planets like Earth. Outside our solar system, some gas giant planets have been detected in the habitable zone of their stars. Their wakes may harbour rocky, Earth-size worlds.

Place, publisher, year, edition, pages
Uppsala: Universitetsbiblioteket, 2009. viii, 102 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 593
Keyword
accretion, accretion disks, hydrodynamics, instabilities, methods: numerical, solar system: formation, planets and satellites: formation, magnetohydrodynamics (MHD), turbulence, diffusion, stars: planetary systems: formation
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-9537 (URN)978-91-554-7395-2 (ISBN)
Public defence
2009-02-26, Polhemsalem, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 14:00
Opponent
Supervisors
Available from: 2009-02-05 Created: 2009-02-05Bibliographically approved

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