scholarly journals Gravitoviscous protoplanetary disks with a dust component

2020 ◽  
Vol 637 ◽  
pp. A5 ◽  
Author(s):  
Vardan G. Elbakyan ◽  
Anders Johansen ◽  
Michiel Lambrechts ◽  
Vitaly Akimkin ◽  
Eduard I. Vorobyov
Keyword(s):  
Surface Density ◽  
Planet Formation ◽  
Gravitational Instability ◽  
Protoplanetary Disks ◽  
Dust Particles ◽  
Circumstellar Disk ◽  
Power Law Distribution ◽  
Momentum Exchange ◽  
Disk Formation ◽  
Dust Component

Aims. We study the dynamics and growth of dust particles in circumstellar disks of different masses that are prone to gravitational instability during the critical first Myr of their evolution. Methods. We solved the hydrodynamics equations for a self-gravitating and viscous circumstellar disk in a thin-disk limit using the FEOSAD numerical hydrodynamics code. The dust component is made up of two different components: micron-sized dust and grown dust of evolving size. For the dust component, we considered the dust coagulation, fragmentation, momentum exchange with the gas, and dust self-gravity. Results. We found that the micron-sized dust particles grow rapidly in the circumstellar disk, reaching a few cm in size in the inner 100 au of the disk during less than 100 kyr after the disk formation, provided that fragmentation velocity is 30 ms−1. Due to the accretion of micron dust particles from the surrounding envelope, which serves as a micron dust reservoir, the approximately cm-sized dust particles continue to be present in the disk for more than 900 kyr after the disk formation and maintain a dust-to-gas ratio close to 0.01. We show that a strong correlation exists between the gas and pebble fluxes in the disk. We find that radial surface density distribution of pebbles in the disk shows power-law distribution with an index similar to that of the Minimum-mass solar nebula regardless the disk mass. We also show that the gas surface density in our models agrees well with measurements of dust in protoplanetary disks of AS 209, HD 163296, and DoAr 25 systems. Conclusions. Pebbles are formed during the very early stages of protoplanetary disk evolution. They play a crucial role in the planet formation process. Our disc simulations reveal the early onset (<105 yr) of an inwards-drifting flux of pebble-sized particles that makes up approximately between one hundredth and one tenth of the gas mass flux, which appears consistent with mm-observations of discs. Such a pebble flux would allow for the formation of planetesimals by streaming instability and the early growth of embryos by pebble accretion. We conclude that unlike the more common studies of isolated steady-state protoplanetary disks, more sophisticated global numerical simulations of circumstellar disk formation and evolution, including the pebble formation from the micron dust particles, are needed for performing realistic planet formation studies.

scholarly journals Gravitoviscous protoplanetary disks with a dust component

2019 ◽  
Vol 631 ◽  
pp. A1 ◽  
Author(s):  
Eduard I. Vorobyov ◽  
Vardan G. Elbakyan
Keyword(s):  
Gravitational Instability ◽  
Protoplanetary Disks ◽  
Maximum Radius ◽  
Order Of Magnitude ◽  
Dust Component ◽  
Tidal Torques ◽  
Self Gravity ◽  
Small Dust ◽  
Collapse Phase ◽  
Hydrodynamics Equations

Aims. Spatial distribution and growth of dust in a clumpy protoplanetary disk subject to vigorous gravitational instability and fragmentation is studied numerically with sub-au resolution using the FEOSAD code. Methods. Hydrodynamics equations describing the evolution of self-gravitating and viscous protoplanetary disks in the thin-disk limit were modified to include a dust component consisting of two parts: sub-micron-sized dust and grown dust with a variable maximum radius. The conversion of small to grown dust, dust growth, friction of dust with gas, and dust self-gravity were also considered. Results. We found that the disk appearance is notably time-variable with spiral arms, dusty rings, and clumps, constantly forming, evolving, and decaying. As a consequence, the total dust-to-gas mass ratio is highly non-homogeneous throughout the disk extent, showing order-of-magnitude local deviations from the canonical 1:100 value. Gravitationally bound clumps formed through gravitational fragmentation have a velocity pattern that deviates notably from the Keplerian rotation. Small dust is efficiently converted into grown dust in the clump interiors, reaching a maximum radius of several decimeters. Concurrently, grown dust drifts towards the clump center forming a massive compact central condensation (70–100 M⊕). We argue that protoplanets may form in the interiors of inward-migrating clumps before they disperse through the action of tidal torques. We foresee the formation of protoplanets at orbital distances of several tens of au with initial masses of gas and dust in the protoplanetary seed in the (0.25–1.6) MJup and (1.0–5.5) M⊕ limits, respectively. The final masses of gas and dust in the protoplanets may however be much higher due to accretion from surrounding massive metal-rich disks/envelopes. Conclusions. Dusty rings formed through tidal dispersal of inward-migrating clumps may have a connection to ring-like structures found in youngest and massive protoplanetary disks. Numerical disk models with a dust component that can follow the evolution of gravitationally bound clumps through their collapse phase to the formation of protoplanets are needed to make firm conclusions on the characteristics of planets forming through gravitational fragmentation.

scholarly journals TW Hya: an old protoplanetary disc revived by its planet

2020 ◽  
Author(s):  
Sergei Nayakshin ◽  
Takashi Tsukagoshi ◽  
Cassandra Hall ◽  
Allona Vazan ◽  
Ravit Helled ◽  
...  
Keyword(s):  
Planet Formation ◽  
Gravitational Instability ◽  
Giant Planet ◽  
Emission Feature ◽  
Time Dependent ◽  
Dust Particles ◽  
Dark Ring ◽  
Build Time ◽  
Core Accretion ◽  
Protoplanetary Discs

Abstract Dark rings with bright rims are the indirect signposts of planets embedded in protoplanetary discs. In a recent first, an azimuthally elongated AU-scale blob, possibly a planet, was resolved with ALMA in TW Hya. The blob is at the edge of a cliff-like rollover in the dust disc rather than inside a dark ring. Here we build time-dependent models of TW Hya disc. We find that the classical paradigm cannot account for the morphology of the disc and the blob. We propose that ALMA-discovered blob hides a Neptune mass planet losing gas and dust. We show that radial drift of mm-sized dust particles naturally explains why the blob is located on the edge of the dust disc. Dust particles leaving the planet perform a characteristic U-turn relative to it, producing an azimuthally elongated blob-like emission feature. This scenario also explains why a 10 Myr old disc is so bright in dust continuum. Two scenarios for the dust-losing planet are presented. In the first, a dusty pre-runaway gas envelope of a ∼40 M⊕ Core Accretion planet is disrupted, e.g., as a result of a catastrophic encounter. In the second, a massive dusty pre-collapse gas giant planet formed by Gravitational Instability is disrupted by the energy released in its massive core. Future modelling may discriminate between these scenarios and allow us to study planet formation in an entirely new way – by analysing the flows of dust and gas recently belonging to planets, informing us about the structure of pre-disruption planetary envelopes.

scholarly journals First Results from the Disk Eclipse Search with KELT (DESK) Survey

2015 ◽  
Vol 10 (S314) ◽  
pp. 167-170 ◽  
Author(s):  
Joseph E. Rodriguez ◽  
Joshua Pepper ◽  
Keivan G. Stassun
Keyword(s):  
Time Series ◽  
Planet Formation ◽  
Protoplanetary Disks ◽  
Young Stars ◽  
Circumstellar Disk ◽  
Core Composition ◽  
Disk Material ◽  
First Results ◽  
Stellar Associations

AbstractUsing time-series photometry from the Kilodegree Extremely Little Telescope (KELT) exoplanet survey, we are looking for eclipses of stars by their protoplanetary disks, specifically in young stellar associations. To date, we have discovered two previously unknown, large dimming events around the young stars RW Aurigae and V409 Tau. We attribute the dimming of RW Aurigae to an occultation by its tidally disrupted disk, with the disruption perhaps resulting from a recent flyby of its binary companion. Even with the dynamical environment of RW Aurigae, the distorted disk material remains very compact and presumably capable of forming planets. This system also shows that strong binary interactions with disks can also influence planet and core composition by stirring up and mixing materials during planet formation. We interpret the dimming of V409 Tau to be due to a feature, possibly a warp or perturbation, lying at least 10 AU from the host star in its nearly edge-on circumstellar disk.

scholarly journals Gravitoviscous protoplanetary disks with a dust component

2019 ◽  
Vol 627 ◽  
pp. A154 ◽  
Author(s):  
Eduard I. Vorobyov ◽  
Aleksandr M. Skliarevskii ◽  
Vardan G. Elbakyan ◽  
Yaroslav Pavlyuchenkov ◽  
Vitaly Akimkin ◽  
...  
Keyword(s):  
Mass Transport ◽  
Gravitational Instability ◽  
Protoplanetary Disks ◽  
Circumstellar Disks ◽  
Appreciable Effect ◽  
Streaming Instability ◽  
T Tauri ◽  
Dust Component ◽  
Cloud Cores ◽  
Slow Transport

Aims. The central region of a circumstellar disk is difficult to resolve in global numerical simulations of collapsing cloud cores, but its effect on the evolution of the entire disk can be significant. Methods. We used numerical hydrodynamics simulations to model the long-term evolution of self-gravitating and viscous circumstellar disks in the thin-disk limit. Simulations start from the gravitational collapse of pre-stellar cores of 0.5–1.0 M⊙ and both gaseous and dusty subsystems were considered, including a model for dust growth. The inner unresolved 1.0 au of the disk is replaced with a central smart cell (CSC), a simplified model that simulates physical processes that may occur in this region. Results. We found that the mass transport rate through the CSC has an appreciable effect on the evolution of the entire disk. Models with slow mass transport form more massive and warmer disks, and are more susceptible to gravitational instability and fragmentation, including a newly identified episodic mode of disk fragmentation in the T Tauri phase of disk evolution. Models with slow mass transport through the CSC feature episodic accretion and luminosity bursts in the early evolution, while models with fast transport are characterized by a steadily declining accretion rate with low-amplitude flickering. Dust grows to a larger, decimeter size in the slow transport models and efficiently drifts in the CSC, where it accumulates and reaches the limit where a streaming instability becomes operational. We argue that gravitational instability, together with a streaming instability likely operating in the inner disk regions, constitute two concurrent planet-forming mechanisms, which may explain the observed diversity of exoplanetary orbits. Conclusions. We conclude that sophisticated models of the inner unresolved disk regions should be used when modeling the formation and evolution of gaseous and dusty protoplanetary disks.

scholarly journals Accretion bursts in magnetized gas-dust protoplanetary disks

2020 ◽  
Vol 644 ◽  
pp. A74
Author(s):  
Eduard I. Vorobyov ◽  
Sergey Khaibrakhmanov ◽  
Shantanu Basu ◽  
Marc Audard
Keyword(s):  
Magnetic Flux ◽  
Dead Zone ◽  
Protoplanetary Disks ◽  
Occurrence Frequency ◽  
Dust Particles ◽  
Back Reaction ◽  
Disk Formation ◽  
Ionization Fraction ◽  
The Dead ◽  
Dust Disks

Aims. Accretion bursts triggered by the magnetorotational instability (MRI) in the innermost disk regions were studied for protoplanetary gas-dust disks that formed from prestellar cores of a various mass Mcore and mass-to-magnetic flux ratio λ. Methods. Numerical magnetohydrodynamics simulations in the thin-disk limit were employed to study the long-term (~1.0 Myr) evolution of protoplanetary disks with an adaptive turbulent α-parameter, which explicitly depends on the strength of the magnetic field and ionization fraction in the disk. The numerical models also feature the co-evolution of gas and dust, including the back-reaction of dust on gas and dust growth. Results. A dead zone with a low ionization fraction of x≲10−13 and temperature on the order of several hundred Kelvin forms in the inner disk soon after its formation, extending from several to several tens of astronomical units depending on the model. The dead zone features pronounced dust rings that are formed due to the concentration of grown dust particles in the local pressure maxima. Thermal ionization of alkaline metals in the dead zone trigger the MRI and associated accretion burst, which is characterized by a sharp rise, small-scale variability in the active phase, and fast decline once the inner MRI-active region is depleted of matter. The burst occurrence frequency is highest in the initial stages of disk formation and is driven by gravitational instability (GI), but it declines with diminishing disk mass-loading from the infalling envelope. There is a causal link between the initial burst activity and the strength of GI in the disk fueled by mass infall from the envelope. We find that the MRI-driven burst phenomenon occurs for λ = 2–10, but diminishes in models with Mcore ≲ M⊙, suggesting a lower limit on the stellar mass for which the MRI-triggered burst can occur. Conclusions. The MRI-triggered bursts occur for a wide range of mass-to-magnetic flux ratios and initial cloud core masses. The burst occurrence frequency is highest in the initial disk formation stage and reduces as the disk evolves from a gravitationally unstable to a viscous-dominated state. The MRI-triggered bursts are intrinsically connected with the dust rings in the inner disk regions, and both can be a manifestation of the same phenomenon, that is to say the formation of a dead zone.

scholarly journals Trapping dust particles in the outer regions of protoplanetary disks

2012 ◽  
Vol 538 ◽  
pp. A114 ◽  
Author(s):  
P. Pinilla ◽  
T. Birnstiel ◽  
L. Ricci ◽  
C. P. Dullemond ◽  
A. L. Uribe ◽  
...  
Keyword(s):  
Protoplanetary Disks ◽  
Dust Particles

scholarly journals Deep 10 and 18 Micron Imaging of the HR 4796A Circumstellar Disk: Transient Dust Particles and Tentative Evidence for a Brightness Asymmetry

2000 ◽  
Vol 530 (1) ◽  
pp. 329-341 ◽  
Author(s):  
C. M. Telesco ◽  
R. S. Fisher ◽  
R. K. Pina ◽  
R. F. Knacke ◽  
S. F. Dermott ◽  
...  
Keyword(s):  
Dust Particles ◽  
Circumstellar Disk ◽  
Tentative Evidence

scholarly journals Streaming instability of multiple particle species in protoplanetary disks

2018 ◽  
Vol 618 ◽  
pp. A75 ◽  
Author(s):  
Noemi Schaffer ◽  
Chao-Chin Yang ◽  
Anders Johansen
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Protoplanetary Disks ◽  
Single Species ◽  
Stokes Number ◽  
Dust Particles ◽  
Particle Sizes ◽  
Particle Species ◽  
Streaming Instability ◽  
Large Particles

The radial drift and diffusion of dust particles in protoplanetary disks affect both the opacity and temperature of such disks, as well as the location and timing of planetesimal formation. In this paper, we present results of numerical simulations of particle-gas dynamics in protoplanetary disks that include dust grains with various size distributions. We have considered three scenarios in terms of particle size ranges, one where the Stokes number τs = 10−1−100, one where τs = 10−4−10−1, and finally one where τs = 10−3−100. Moreover, we considered both discrete and continuous distributions in particle size. In accordance with previous works we find in our multispecies simulations that different particle sizes interact via the gas and as a result their dynamics changes compared to the single-species case. The larger species trigger the streaming instability and create turbulence that drives the diffusion of the solid materials. We measured the radial equilibrium velocity of the system and find that the radial drift velocity of the large particles is reduced in the multispecies simulations and that the small particle species move on average outwards. We also varied the steepness of the size distribution, such that the exponent of the solid number density distribution, dN∕da ∝ a−q, is either q = 3 or q = 4. Overall, we find that the steepness of the size distribution and the discrete versus continuous approach have little impact on the results. The level of diffusion and drift rates are mainly dictated by the range of particle sizes. We measured the scale height of the particles and observe that small grains are stirred up well above the sedimented midplane layer where the large particles reside. Our measured diffusion and drift parameters can be used in coagulation models for planet formation as well as to understand relative mixing of the components of primitive meteorites (matrix, chondrules and CAIs) prior to inclusion in their parent bodies.

scholarly journals Physical Processes in Cometary Atmospheres

1972 ◽  
Vol 45 ◽  
pp. 253-259 ◽  
Author(s):  
A. Z. Dolginov
Keyword(s):  
Rotation Period ◽  
Dust Particles ◽  
Molecular Flow ◽  
Physical Parameters ◽  
Charged Dust ◽  
Nuclear Surface ◽  
Cometary Dust ◽  
Meteor Streams ◽  
Cometary Tail ◽  
Dust Component

Formulae are obtained for the distribution of molecules in the cometary head, taking into account the conditions of hydrodynamic and free molecular flow in various regions around the nucleus. Experimental data are used to derive physical parameters near the nuclei of comets 1952 III, 1955 V, 1957 III, and 1960 II and the rate of decrease of mass. The possibility of chemical reactions in the region close to the nucleus is discussed. Gas condensation is shown to be a possible cause of dust formation under the conditions existing near the nucleus, and this process may be responsible for the major portion of the cometary dust component. The observed grouping of synchrones in the cometary tail can be explained on the assumption that the nuclear surface comprises two (or more) areas differing essentially in evaporation rate, the amount of matter ejected varying over the rotation period of the nucleus. Charged dust particles are shown to form, with electrons and ions, a common medium, i.e., dust plasma, which can be treated by the same methods used for ordinary plasma. Special investigations appear to be desirable when comets intersect meteor streams.

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