scholarly journals Features of the Dynamical Evolution of a Massive Disk of Trans-Neptunian Objects

2021 ◽  
Vol 55 (4) ◽  
pp. 341-347
Author(s):  
V. V. Emel’yanenko
Keyword(s):  
Gravitational Instability ◽  
Dynamical Behavior ◽  
Dynamical Evolution ◽  
Initial Mass ◽  
Time Interval ◽  
Small Bodies ◽  
Outer Planets ◽  
Hill Region ◽  
Gravitational Influence ◽  
Self Gravity

Abstract— The dynamical features of a massive disk of distant trans-Neptunian objects are considered in the model of the formation of small bodies in the Hill region of a giant gas-dust clump that arose as a result of gravitational instability and fragmentation of the protoplanetary disk. The dynamical evolution of the orbits of small bodies under the action of gravitational perturbations from the outer planets and self-gravity of the disk has been studied for a time interval of the order of a billion years. It is shown that the secular effects of the gravitational influence of a massive disk of small bodies lead to an increase in the eccentricities of the orbits of individual objects. The result of this dynamical behavior is the creation of a flux of small bodies coming close to the orbit of Neptune. The change in the number of objects surviving in the observable region of distant trans-Neptunian objects (the region of orbits with perihelion distances of 40 < q < 80 AU and semimajor axes 150 < a < 1000 AU), over time depends on the initial mass of the disk. For disks with masses exceeding several Earth masses, there is a tendency to a decrease in the number of distant trans-Neptunian objects surviving in the observable region after evolution for a time interval of the order of the age of the Solar System, with an increase in the initial mass. On the other hand, for most objects, orbital eccentricities decrease under the influence of the self-gravity of the disk. Therefore, the main part of the disk is preserved in the region of heliocentric distances exceeding 100 AU.

scholarly journals η Chamaeleontis: abnormal initial mass function or dynamical evolution?

2007 ◽  
Vol 473 (1) ◽  
pp. 163-170 ◽  
Author(s):  
E. Moraux ◽  
W. A. Lawson ◽  
C. Clarke
Keyword(s):  
Dynamical Evolution ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass

scholarly journals Growth after the streaming instability

2019 ◽  
Vol 624 ◽  
pp. A114 ◽  
Author(s):  
Beibei Liu ◽  
Chris W. Ormel ◽  
Anders Johansen
Keyword(s):  
Dynamical Evolution ◽  
Bimodal Distribution ◽  
Stokes Number ◽  
Volume Density ◽  
Mass Star ◽  
Type I ◽  
Solar Mass ◽  
Streaming Instability ◽  
Two Component ◽  
Self Gravity

Context. Streaming instability is a key mechanism in planet formation, clustering pebbles into planetesimals with the help of self-gravity. It is triggered at a particular disk location where the local volume density of solids exceeds that of the gas. After their formation, planetesimals can grow into protoplanets by feeding from other planetesimals in the birth ring as well as by accreting inwardly drifting pebbles from the outer disk. Aims. We aim to investigate the growth of planetesimals into protoplanets at a single location through streaming instability. For a solar-mass star, we test the conditions under which super-Earths are able to form within the lifetime of the gaseous disk. Methods. We modified the Mercury N-body code to trace the growth and dynamical evolution of a swarm of planetesimals at a distance of 2.7 AU from the star. The code simulates gravitational interactions and collisions among planetesimals, gas drag, type I torque, and pebble accretion. Three distributions of planetesimal sizes were investigated: (i) a mono-dispersed population of 400 km radius planetesimals, (ii) a poly-dispersed population of planetesimals from 200 km up to 1000 km, (iii) a bimodal distribution with a single runaway body and a swarm of smaller, 100 km size planetesimals. Results. The mono-dispersed population of 400 km size planetesimals cannot form protoplanets of a mass greater than that of the Earth. Their eccentricities and inclinations are quickly excited, which suppresses both planetesimal accretion and pebble accretion. Planets can form from the poly-dispersed and bimodal distributions. In these circumstances, it is the two-component nature that damps the random velocity of the large embryo through the dynamical friction of small planetesimals, allowing the embryo to accrete pebbles efficiently when it approaches 10−2 M⊕. Accounting for migration, close-in super-Earth planets form. Super-Earth planets are likely to form when the pebble mass flux is higher, the disk turbulence is lower, or the Stokes number of the pebbles is higher. Conclusions. For the single site planetesimal formation scenario, a two-component mass distribution with a large embryo and small planetesimals promotes planet growth, first by planetesimal accretion and then by pebble accretion of the most massive protoplanet. Planetesimal formation at single locations such as ice lines naturally leads to super-Earth planets by the combined mechanisms of planetesimal accretion and pebble accretion.

scholarly journals Spiral-arm instability – III. Fragmentation of primordial protostellar discs

2019 ◽  
Vol 491 (1) ◽  
pp. L24-L28 ◽  
Author(s):  
Shigeki Inoue ◽  
Naoki Yoshida
Keyword(s):  
Gravitational Instability ◽  
Finite Thickness ◽  
Linear Perturbation ◽  
Gas Cooling ◽  
Formation And Evolution ◽  
Linear Perturbation Theory ◽  
The Stability ◽  
Protostellar Discs ◽  
Self Gravity ◽  
Spiral Arm

ABSTRACT We study the gravitational instability and fragmentation of primordial protostellar discs by using high-resolution cosmological hydrodynamics simulations. We follow the formation and evolution of spiral arms in protostellar discs, examine the dynamical stability, and identify a physical mechanism of secondary protostar formation. We use linear perturbation theory based on the spiral-arm instability (SAI) analysis in our previous studies. We improve the analysis by incorporating the effects of finite thickness and shearing motion of arms, and derive the physical conditions for SAI in protostellar discs. Our analysis predicts accurately the stability and the onset of arm fragmentation that is determined by the balance between self-gravity and gas pressure plus the Coriolis force. Formation of secondary and multiple protostars in the discs is explained by the SAI, which is driven by self-gravity and thus can operate without rapid gas cooling. We can also predict the typical mass of the fragments, which is found to be in good agreement with the actual masses of secondary protostars formed in the simulation.

scholarly journals Linear analysis of the non-axisymmetric secular gravitational instability

2019 ◽  
Vol 487 (4) ◽  
pp. 5405-5415
Author(s):  
Mohsen Shadmehri ◽  
Razieh Oudi ◽  
Gohar Rastegarzadeh
Keyword(s):  
Amplification Factor ◽  
Gravitational Instability ◽  
Radial Distance ◽  
Dust Particles ◽  
Linear Perturbation ◽  
Model Parameters ◽  
Time Interval ◽  
Continuous Growth ◽  
Two Fluid ◽  
Axisymmetric Perturbations

Abstract In protoplanetary discs (PPDs) consisting of gas and dust particles, fluid instabilities induced by the drag force, including secular gravitational instability (SGI), can facilitate planet formation. Although SGI subject to the axisymmetric perturbations was originally studied in the absence of gas feedback and it then generalized using a two-fluid approach, the fate of the non-axisymmetric SGI, in either case, is an unexplored problem. We present a linear perturbation analysis of the non-axisymmetric SGI in a PPD by implementing a two-fluid model. We explore the growth of the local, non-axisymmetric perturbations using a set of linearized perturbation equations in a sheared frame. The non-axisymmetric perturbations display a significant growth during a finite time interval even when the system is stable against the axisymmetric perturbations. Furthermore, the surface density perturbations do not show the continuous growth but are temporally amplified. We also study cases where the dust component undergoes amplification whereas the gas component remains stable. The amplitude amplification, however, strongly depends on the model parameters. In the minimum mass solar nebula (MMSN), for instance, the dust fluid amplification at the radial distance 100 au occurs when the Stokes number is about unity. But the amplification factor reduces as the dust and gas coupling becomes weaker. Furthermore, perturbations with a larger azimuthal wavelength exhibit a larger amplification factor.

scholarly journals Global simulations of galactic discs: violent feedback from clustered supernovae during bursts of star formation

2019 ◽  
Vol 492 (1) ◽  
pp. 79-95 ◽  
Author(s):  
Davide Martizzi
Keyword(s):  
Adaptive Mesh Refinement ◽  
Gravitational Instability ◽  
Adaptive Mesh ◽  
Dark Matter Halo ◽  
Time Variability ◽  
Mass Loading ◽  
Star Forming ◽  
Galactic Winds ◽  
Self Gravity ◽  
Supernova Feedback

ABSTRACT A suite of idealized, global, gravitationally unstable, star-forming galactic disc simulations with 2 pc spatial resolution, performed with the adaptive mesh refinement code ramses, is used in this paper to predict the emergent effects of supernova feedback. The simulations include a simplified prescription for the formation of single stellar populations of mass $\sim 100 \, {\rm M}_{\odot }$, radiative cooling, photoelectric heating, an external gravitational potential for a dark matter halo and an old stellar disc, self-gravity, and a novel implementation of supernova feedback. The results of these simulations show that gravitationally unstable discs can generate violent supersonic winds with mass-loading factors η ≳ 10, followed by a galactic fountain phase. These violent winds are generated by highly clustered supernovae exploding in dense environments created by gravitational instability, and they are not produced in simulation without self-gravity. The violent winds significantly perturb the vertical structure of the disc, which is later re-established during the galactic fountain phase. Gas resettles into a quasi-steady, highly turbulent disc with volume-weighted velocity dispersion $\sigma \gt 50 \, {\rm km\, s}^{-1}$. The new configuration drives weaker galactic winds with a mass-loading factor η ≤ 0.1. The whole cycle takes place in ≤10 dynamical times. Such high time variability needs to be taken into account when interpreting observations of galactic winds from starburst and post-starburst galaxies.

scholarly journals Post-rendezvous radar properties of comet 67P/CG from the Rosetta Mission: understanding future Earth-based radar observations and the dynamical evolution of comets

2019 ◽  
Vol 489 (2) ◽  
pp. 1667-1683 ◽  
Author(s):  
Essam Heggy ◽  
Elizabeth M Palmer ◽  
Alain Hérique ◽  
Wlodek Kofman ◽  
M Ramy El-Maarry
Keyword(s):  
Large Scale ◽  
Structural Changes ◽  
Dynamical Evolution ◽  
Textural Properties ◽  
Building Blocks ◽  
Cometary Nucleus ◽  
Small Scale ◽  
Small Bodies ◽  
Radar Observations ◽  
Comet 67P

ABSTRACT Radar observations provide crucial insights into the formation and dynamical evolution of comets. This ability is constrained by our knowledge of the dielectric and textural properties of these small-bodies. Using several observations by Rosetta as well as results from the Earth-based Arecibo radio telescope, we provide an updated and comprehensive dielectric and roughness description of Comet 67P/CG, which can provide new constraints on the radar properties of other nuclei. Furthermore, contrary to previous assumptions of cometary surfaces being dielectrically homogeneous and smooth, we find that cometary surfaces are dielectrically heterogeneous ( εr′≈1.6–3.2), and are rough at X- and S-band frequencies, which are widely used in characterization of small-bodies. We also investigate the lack of signal broadening in CONSERT observations through the comet head. Our results suggest that primordial building blocks in the subsurface are either absent, smaller than the radar wavelength, or have a weak dielectric contrast (Δ εr′). To constrain this ambiguity, we use optical albedo measurements by the OSIRIS camera of the freshly exposed subsurface after the Aswan cliff collapse. We find that the hypothetical subsurface blocks should have |Δ εr′|≳0.15, setting an upper limit of ∼ 1 m on the size of 67P/CG's primordial building blocks if they exist. Our analysis is consistent with a purely thermal origin for the ∼ 3 m surface bumps on pit walls and cliff-faces, hypothesized to be high-centred polygons formed from fracturing of the sintered shallow ice-bearing subsurface due to seasonal thermal expansion and contraction. Potential changes in 67P/CG's radar reflectivity at these at X- and S-bands can be associated with large-scale structural changes of the nucleus rather than small-scale textural ones. Monitoring changes in 67P/CG's radar properties during repeated close-approaches via Earth-based observations can constrain the dynamical evolution of its cometary nucleus.

scholarly journals DYNAMICAL DERIVATION OF BODE'S LAW

2005 ◽  
Vol 14 (01) ◽  
pp. 153-169 ◽  
Author(s):  
R. W. BASS ◽  
A. DEL POPOLO
Keyword(s):  
Angular Momentum ◽  
Total Angular Momentum ◽  
Central Body ◽  
Dynamical Evolution ◽  
Satellite System ◽  
Point Particle ◽  
The Body ◽  
The Sun ◽  
Small Bodies ◽  
Orbital Radius

In a planetary or satellite system, idealized as n small bodies in an initially coplanar with concentric orbits around a large central body obeying the Newtonian point-particle mechanics, resonant perturbations will cause a dynamical evolution of the orbital radii except for cases with highly specific mutual relationships. In particular, the most stable situation can be achieved only when each planetary orbit is roughly twice as far from the Sun as the preceding one. This has been empirically observed by Titius (1766) and Bode (1778). By reformulating the problem as a hierarchical sequence of (unrestricted) 3-body problems and considering only the gravitational interactions among the central body and the body of interest and the adjacent outer body in the orbits, it is proved that the resonant perturbations from the outer body will destabilize the inner body (and vice versa) unless its mean orbital radius is a unique and specific multiple of β, the distal multiplier, of the inner body. In this way a sequence of concentric orbits can each stabilize the adjacent inner orbit, and since the outermost orbit is already tied to the collection of the inner orbits by conservation of total angular momentum, the entire configuration is stabilized.

scholarly journals Improved dynamical modelling of the Arches cluster

2013 ◽  
Vol 9 (S303) ◽  
pp. 59-60
Author(s):  
Joowon Lee ◽  
Sungsoo S. Kim
Keyword(s):  
Surface Brightness ◽  
Massive Star ◽  
Velocity Dispersion ◽  
Galactic Center ◽  
Dynamical Evolution ◽  
Star Cluster ◽  
Initial Mass ◽  
Data Set ◽  
Cluster A ◽  
Best Fit

AbstractRecently, Clarkson et al. (2012) measured the intrinsic velocity dispersion of the Arches cluster, a young and massive star cluster in the Galactic center. Using the observed velocity dispersion profile and the surface brightness profile of Espinoza et al. (2009), they estimate the cluster's present-day mass to be ∼ 1.5×104 M⊙ by fitting an isothermal King model. In this study, we trace the best-fit initial mass for the Arches cluster using the same observed data set and also the anisotropic Fokker-Planck calculations for the dynamical evolution.

scholarly journals Orbital features of distant trans-Neptunian objects induced by giant gaseous clumps

2020 ◽  
Vol 642 ◽  
pp. L20
Author(s):  
V. V. Emel’yanenko
Keyword(s):  
Simple Model ◽  
Solar Nebula ◽  
Dynamical Evolution ◽  
Outer Solar System ◽  
The Sun ◽  
High Eccentricity ◽  
Small Bodies ◽  
Dynamical Characteristics ◽  
Gravitational Perturbations ◽  
The Hill

Context. The discovery of distant trans-Neptunian objects has led to heated discussions about the structure of the outer Solar System. Aims. We study the dynamical evolution of small bodies from the Hill regions of migrating giant gaseous clumps that form in the outer solar nebula via gravitational fragmentation. We attempt to determine whether the observed features of the orbital distribution of distant trans-Neptunian objects could be caused by this process. Methods. We consider a simple model that includes the Sun, two point-like giant clumps with masses of ∼10 Jupiter masses, and a set of massless objects initially located in the Hill regions of these clumps. We carry out numerical simulations of the motions of small bodies under gravitational perturbations from two giant clumps that move in elliptical orbits and approach each other. The orbital distribution of these small bodies is compared with the observed distribution of distant trans-Neptunian objects. Results. In addition to the known grouping in longitudes of perihelion, we note new features for observed distant trans-Neptunian objects. The observed orbital distribution points to the existence of two groups of distant trans-Neptunian objects with different dynamical characteristics. We show that the main features of the orbital distribution of distant trans-Neptunian objects can be explained by their origin in the Hill regions of migrating giant gaseous clumps. Small bodies are ejected from the Hill regions when the giant clumps move in high-eccentricity orbits and have a close encounter with each other. Conclusions. The resulting orbital distribution of small bodies in our model and the observed distribution of distant trans-Neptunian objects have similar features.

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