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1.
Sebastian Wolf 《Astrophysics and Space Science》2008,313(1-3):109-112
Theoretical investigations show that planet-disk interactions cause structures in circumstellar disks, which are usually much
larger in size than the planet itself and thus more easily detectable. The specific result of planet-disk interactions depends
on the evolutionary stage of the disk. Exemplary signatures of planets embedded in disks are gaps and spiral density waves
in the case of young, gas-rich protoplanetary disks and characteristic asymmetric density patterns in debris disks. Numerical
simulations convincingly demonstrate that high-resolution imaging performed with observational facilities which are already
available or will become available in the near future will allow to trace these “fingerprints” of planets in protoplanetary
and debris disks. These observations will provide a deep insight into specific phases of the formation and early evolution
of planets in circumstellar disks.
In this context, the Atacama Large Millimeter Array (ALMA) will play a crucial role by allowing to trace features in disks
which are indicative for various stages of the formation and early evolution of planets in circumstellar disks. 相似文献
2.
Dániel Apai 《Earth, Moon, and Planets》2009,105(2-4):311-320
The study of planet formation is a field that uniquely benefits from both astronomical observations and laboratory studies of primitive meteoritic material left over from the forming Solar System. We concisely review the key constraints from these studies and place them in the frame of the theoretical models. Four major open problems are identified that can be addressed with next-generation ground-based telescopes: (1) The injection of radionucleids to protoplanetary disks; (2) Protostellar collapse and the formation of the first solids; (3) Thermal processing of protoplanetary materials; (4) Disk–planet interactions and disk dispersal. 相似文献
3.
《Planetary and Space Science》2007,55(5):569-581
We discuss selected possibilities to detect planets in circumstellar disks. We consider the search for characteristic signatures in these disks caused by the interaction of giant planets with the disk as the most promising approach. Numerical simulations show that these signatures are usually much larger in size than the planet itself and thus much easier to detect. The particular result of the planet–disk interaction depends on the evolutionary stage of the disk. Primary signatures of planets embedded in disks are gaps in the case of young disks and characteristic asymmetric density patterns in debris disks.We present simulations which demonstrate that high spatial resolution observations performed with instruments/telescopes that will become available in the near future will be able to trace the location and other properties of young and evolved planets. These observations will allow to directly investigate the formation and evolution of planets in protoplanetary and debris disks. 相似文献
4.
Most main sequence stars are binaries or higher multiplicity Systems and it appears that at birth most stars have circumstellar
disks. It is commonly accepted that planetary systems arise from the material of these disks; consequently, binary and multiple
systems may have a main role in planet formation. In this paper, we study the stage of planetary formation during which the
particulate material is still dispersed as centimetre-to-metre sized primordial aggregates. We investigate the response of
the particles, in a protoplanetary disk with radius RD = 100 AU around a solar-like star, to the gravitational field of bound perturbing companions in a moderately wide (300–1600
AU) orbit. For this purpose, we have carried out a series of simulations of coplanar hierarchical configurations using a direct
integration code that models gravitational and viscous forces. The massive protoplanetary disk is around one of the components
of the binary. The evolution in time of the dust sub-disk depends mainly on the nature (prograde or retrograde) of the relative
revolution of the stellar companion, and on the temperature and mass of the circumstellar disk. Our results show that for
binary companions near the limit of tidal truncation of the disk, the perturbation leads to an enhanced accretion rate onto
the primary, decreasing the lifetime of the particles in the protoplanetary disk with respect to the case of a single star.
As a consequence of an enhanced accretion rate the mass of the disk decreases faster, which leads to a longer resultant lifetime
for particles in the disk. On the other hand, binary companions may induce tidal arms in the dust phase of protoplanetary
disks. Spiral perturbations with m = 1 may increase in a factor 10 or more the dust surface density in the neighbourhood of
the arm, facilitating the growth of the particles. Moreover, in a massive disk (0.01M⊙) the survival time of particles is
significantly shorter than in a less massive nebula (0.001M⊙) and the temperature of the disk severely influences the spiral-in
time of particles. The rapid evolution of the dust component found in post T Tauri stars can be explained as a result of their
binary nature. Binarity may also influence the evolution of circumpulsar disks.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
We model the growth of Jupiter via core nucleated accretion, applying constraints from hydrodynamical processes that result from the disk-planet interaction. We compute the planet's internal structure using a well tested planetary formation code that is based upon a Henyey-type stellar evolution code. The planet's interactions with the protoplanetary disk are calculated using 3-D hydrodynamic simulations. Previous models of Jupiter's growth have taken the radius of the planet to be approximately one Hill sphere radius, RH. However, 3-D hydrodynamic simulations show that only gas within ∼0.25RH remains bound to the planet, with the more distant gas eventually participating in the shear flow of the protoplanetary disk. Therefore in our new simulations, the planet's outer boundary is placed at the location where gas has the thermal energy to reach the portion of the flow not bound to the planet. We find that the smaller radius increases the time required for planetary growth by ∼5%. Thermal pressure limits the rate at which a planet less than a few dozen times as massive as Earth can accumulate gas from the protoplanetary disk, whereas hydrodynamics regulates the growth rate for more massive planets. Within a moderately viscous disk, the accretion rate peaks when the planet's mass is about equal to the mass of Saturn. In a less viscous disk hydrodynamical limits to accretion are smaller, and the accretion rate peaks at lower mass. Observations suggest that the typical lifetime of massive disks around young stellar objects is ∼3 Myr. To account for the dissipation of such disks, we perform some of our simulations of Jupiter's growth within a disk whose surface gas density decreases on this timescale. In all of the cases that we simulate, the planet's effective radiating temperature rises to well above 1000 K soon after hydrodynamic limits begin to control the rate of gas accretion and the planet's distended envelope begins to contract. According to our simulations, proto-Jupiter's distended and thermally-supported envelope was too small to capture the planet's current retinue of irregular satellites as advocated by Pollack et al. [Pollack, J.B., Burns, J.A., Tauber, M.E., 1979. Icarus 37, 587-611]. 相似文献
6.
《天文和天体物理学研究(英文版)》2020,(10)
The characterization of exoplanets and their birth protoplanetary disks has enormously advanced in the last decade. Benefitting from that, our global understanding of the planet formation processes has been substantially improved. In this review, we first summarize the cutting-edge states of the exoplanet and disk observations. We further present a comprehensive panoptic view of modern core accretion planet formation scenarios, including dust growth and radial drift, planetesimal formation by the streaming instability, core growth by planetesimal accretion and pebble accretion. We discuss the key concepts and physical processes in each growth stage and elaborate on the connections between theoretical studies and observational revelations. Finally, we point out the critical questions and future directions of planet formation studies. 相似文献
7.
T. V. Demidova 《Solar System Research》2018,52(2):180-188
The formation of a planetary system from the protoplanetary disk leads to destruction of the latter; however, a debris disk can remain in the form of asteroids and cometary material. The motion of planets can cause the formation of coorbital structures from the debris disk matter. Previous calculations have shown that such a ring-like structure is more stable if there is a binary star in the center of the system, as opposed to a single star. To analyze the properties of the coorbital structure, we have calculated a grid of models of binary star systems with a circumbinary planet moving in a planetesimal disk. The calculations are performed considering circular orbits of the stars and the planet; the mass and position of the planet, as well as the mass ratio of the stars, are varied. The analysis of the models shows that the width of the coorbital ring and its stability significantly depend on the initial parameters of the problem. Additionally, the empirical dependences of the width of the coorbital structure on the parameters of the system have been obtained, and the parameters of the models with the most stable coorbital structures have been determined. The results of the present study can be used for the search of planets around binary stars with debris disks. 相似文献
8.
This review presents recent results on protoplanetary disks obtained from angularly resolved observations. Observations with mm arrays show that disks are in Keplerian rotation, with radius as large as 1000 AU. Optical images show disks to be flared. Both type of observations imply the dust in disk has evolved and grown from interstellar dust. Measurement of the gas temperature from CO isotopes indicate temperature gradient, consistent with the disk flaring and heating by the central star. Disks which appear to have started to dissipate their initial gas content have also been discovered, but their very diverse aspects leaves the dissipation process unclear. Current data mostly concern the outer disk (>50 AU), although near-IR interferometry has started to unveil the innermost regions (<1 AU). The next generation of instruments (MIDI on VLTI, ALMA) will allow to probe the intermediate regime, where planet formation is expected to occur. 相似文献
9.
We compute the growth of isolated gaseous giant planets for several values of the density of the protoplanetary disk, several distances from the central star and two values for the (fixed) radii of accreted planetesimals. Calculations were performed in the frame of the core instability mechanism and the solids accretion rate adopted is that corresponding to the oligarchic growth regime. We find that for massive disks and/or for protoplanets far from the star and/or for large planetesimals, the planetary growth occurs smoothly. However, notably, there are some cases for which we find an envelope instability in which the planet exchanges gas with the surrounding protoplanetary nebula. The timescale of this instability shows that it is associated with the process of planetesimals accretion. The presence of this instability makes it more difficult the formation of gaseous giant planets. 相似文献
10.
S. I. Ipatov 《Earth, Moon, and Planets》1987,39(2):101-128
Within the model of solid-body accumulation of planets (or their nuclei) the accumulation and migration of bodies from the feeding zones of the giant planets are investigated. The investigation is based on results of computer simulation of evolving disks which initially consisted of hundreds of particles moving about the Sun and coagulating under collisions. In some models the disks initially consisted of identical bodies. In other models they included also almost-formed planets. The computer simulation results as well as analytical investigations of the disk evolution depending on the number of particles in the disk allowed some estimates and conclusions on the accumulation process when the number of initial bodies was great (~ 106–1012). In this paper the characteristics of an initial protoplanetary circumsolar cloud, the body migration in the forming solar system, the planet orbit evolution, the formation of the beyond-Neptune belt and asteroid belts between the giant planet orbits are considered. The results obtained confirm many analytical estimates earlier made by V. S. Safronov and his colleagues. 相似文献
11.
Jonathan P. WILLIAMS 《Meteoritics & planetary science》2012,47(12):1915-1921
Abstract– I summarize recent surveys of protoplanetary disks at millimeter wavelengths and show that the distribution of luminosity, equivalent to the mass in small dust grains, declines rapidly. This contrasts with statistics on the lifetime of disks from infrared observations and the high occurrence of planets from radial velocity and transit surveys. I suggest that these disparate results can be reconciled if most of the dust in a disk is locked up in millimeter and larger‐sized particles within about 2 Myr. This statistical result on disk evolution agrees with detailed modeling of a small number of individual disks and with cosmochemical measurements of rapid planetesimal formation. 相似文献
12.
Astronomical observations have shown that protoplanetary disks are dynamic objects through which mass is transported and accreted by the central star. This transport causes the disks to decrease in mass and cool over time, and such evolution is expected to have occurred in our own solar nebula. Age dating of meteorite constituents shows that their creation, evolution, and accumulation occupied several Myr, and over this time disk properties would evolve significantly. Moreover, on this timescale, solid particles decouple from the gas in the disk and their evolution follows a different path. It is in this context that we must understand how our own solar nebula evolved and what effects this evolution had on the primitive materials contained within it. Here we present a model which tracks how the distribution of water changes in an evolving disk as the water-bearing species experience condensation, accretion, transport, collisional destruction, and vaporization. Because solids are transported in a disk at different rates depending on their sizes, the motions will lead to water being concentrated in some regions of a disk and depleted in others. These enhancements and depletions are consistent with the conditions needed to explain some aspects of the chemistry of chondritic meteorites and formation of giant planets. The levels of concentration and depletion, as well as their locations, depend strongly on the combined effects of the gaseous disk evolution, the formation of rapidly migrating rubble, and the growth of immobile planetesimals. Understanding how these processes operate simultaneously is critical to developing our models for meteorite parent body formation in the Solar System and giant planet formation throughout the galaxy. We present examples of evolution under a range of plausible assumptions and demonstrate how the chemical evolution of the inner region of a protoplanetary disk is intimately connected to the physical processes which occur in the outer regions. 相似文献
13.
In this lecture, we review the properties of protoplanetary disks as derived from high angular resolution observations at millimeter wavelengths. We discuss how the combination of several different high angular resolution techniques allow us to probe different regions of the disk around young stellar objects and to derive the properties of the dust when combined with sophisticated disk models. The picture that emerges is that the dust in circumstellar disks surrounding pre-main sequence stars is in many cases significantly evolved compared to the dust in molecular clouds and the interstellar medium. It is however still difficult to derive a consistent picture and timeline for dust evolution in disks as the observations are still limited to small samples of objects.We also review the evidence for and properties of disks around high-mass young stellar objects and the implications on their formation mechanisms. The study of massive YSOs is complicated by their short lifetimes and larger average distances. In most cases high angular resolution data at millimeter wavelengths are the only method to probe the structure of disks in these objects.We provide a summary of the characteristics of available high angular resolution millimeter and submillimeter observatories. We also describe the characteristics of the ALMA observatory being constructed in the Chilean Andes. ALMA is going to be the world leading observatory at millimeter wavelengths in the coming decades, the project is now in its main construction phase with early science activities envisaged for 2010 and full science operations for 2012. 相似文献
14.
We have constructed a model of the solar nebula that allows for the temperature and pressure distributions at various stages
of its evolution to be calculated. The mass flux from the accretion envelope to the disk and from the disk to the Sun, the
turbulent viscosity parameter α, the opacity of the disk material, and the initial angular momentum of the protosun are the
input model parameters that are varied. We also take into account the changes in the luminosity and radius of the young Sun.
The input model parameters are based mostly on data obtained from observations of young solar-type stars with disks. To correct
the input parameters, we use the mass and chemical composition of Jupiter, as well as models of its internal structure and
formation that allow constraints to be imposed on the temperature and surface density of the protoplanetary disk in Jupiter’s
formation zone. Given the derived constraints on the input parameters, we have calculated models of the solar nebula at successive
stages of its evolution: the formation inside the accretion envelope, the evolution around the young Sun going through the
T Tauri stage, and the formation and compaction of a thin dust layer (subdisk) in the disk midplane. We have found the following
evolutionary trend: an increase in the temperature of the disk at the stage of its formation, cooling at the T Tauri stage,
and the subsequent internal heating of the dust subdisk by turbulence dissipation that causes a temperature rise in the formation
zone of the terrestrial planets at the high subdisk density and the opacity in this zone. We have obtained the probable ranges
of temperatures in the disk midplane, i.e., the temperatures of the protoplanetary material in the formation region of the
terrestrial planets at the initial stage of their formation. 相似文献
15.
J. C. B. Papaloizou 《Celestial Mechanics and Dynamical Astronomy》2016,126(1-3):157-187
We study orbital evolution of multi-planet systems with masses in the terrestrial planet regime induced through tidal interaction with a protoplanetary disk assuming that this is the dominant mechanism for producing orbital migration and circularization. We develop a simple analytic model for a system that maintains consecutive pairs in resonance while undergoing orbital circularization and migration. This model enables migration times for each planet to be estimated once planet masses, circularization times and the migration time for the innermost planet are specified. We applied it to a system with the current architecture of Kepler 444 adopting a simple protoplanetary disk model and planet masses that yield migration times inversely proportional to the planet mass, as expected if they result from torques due to tidal interaction with the protoplanetary disk. Furthermore the evolution time for the system as a whole is comparable to current protoplanetary disk lifetimes. In addition we have performed a number of numerical simulations with input data obtained from this model. These indicate that although the analytic model is inexact, relatively small corrections to the estimated migration rates yield systems for which period ratios vary by a minimal extent. Because of relatively large deviations from exact resonance in the observed system of up to 2 %, the migration times obtained in this way indicate only weak convergent migration such that a system for which the planets did not interact would contract by only \({\sim }1\,\%\) although undergoing significant inward migration as a whole. We have also performed additional simulations to investigate conditions under which the system could undergo significant convergent migration before reaching its final state. These indicate that migration times have to be significantly shorter and resonances between planet pairs significantly closer during such an evolutionary phase. Relative migration rates would then have to decrease allowing period ratios to increase to become more distant from resonances as the system approached its final state in the inner regions of the protoplanetary disk. 相似文献
16.
17.
S. Kraus 《Astronomische Nachrichten》2014,335(1):51-58
Modern optical spectrographs and optical interferometers push the limits in the spectral and spatial regime, providing important new tools for the exploration of the Universe. In this contribution I outline the complementary nature of spectroscopic and interferometric observations and discuss different strategies for combining such data. Most remarkable, the latest generation of “spectro‐interferometric” instruments combine the milliarcsecond angular resolution achievable with interferometry with spectral capabilities, enabling direct constraints on the distribution, density, kinematics, and ionization structure of the gas component in protoplanetary disks. I will present some selected studies from the field of star‐ and planet formation and hot star research in order to illustrate these fundamentally new observational opportunities. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
F.J. Ciesla 《Icarus》2009,200(2):655-671
Large-scale radial transport of solids appears to be a fundamental consequence of protoplanetary disk evolution based on the presence of high temperature minerals in comets and the outer regions of protoplanetary disks around other stars. Further, inward transport of solids from the outer regions of the solar nebula has been postulated to be the manner in which short-lived radionuclides were introduced to the terrestrial planet region and the cause of the variations in oxygen isotope ratios in the primitive materials. Here, both outward and inward transport of solids are investigated in the context of a two-dimensional, viscously evolving protoplanetary disk. The dynamics of solids are investigated to determine how they depend on particle size and the particular stage of protoplanetary disk evolution, corresponding to different rates of mass transport. It is found that the outward flows that arise around the disk midplane of a protoplanetary disk aid in the outward transport of solids up to the size of CAIs s and can increase the crystallinity fraction of silicate dust at 10 AU around a solar mass star to as much as ∼40% in the case of rapidly evolving disks, decreasing as the accretion rate onto the star slows. High velocity, inward flows along the disk surface aid in the rapid transport of solids from the outer disk to the inner disk, particularly for small dust. Despite the diffusion that occurs throughout the disk, the large-scale, meridonal flows associated with mass transport prevent complete homogenization of the disk, allowing compositional gradients to develop that vary in intensity for a timescale of one million of years. The variations in the rates and the preferred direction of radial transport with height above the disk midplane thus have important implications for the dynamics and chemical evolution of primitive materials. 相似文献
19.
Truswin Raksasataya Ana-Ines Gomez de Castro Laurent Koechlin Jean-Pierre Rivet 《Experimental Astronomy》2011,30(2-3):183-194
The Fresnel Diffractive Imager concept is proposed for space borne astronomical imaging at Ultra-Violet wavelengths, using diffractive focalization. The high angular resolution and high dynamic range provided by this new concept makes it an ideal tool to resolve circumstellar structures such as disks or jets around bright sources, among them, pre-main sequence stars and young planetary disks. The study presented in this paper addresses the following configuration of Fresnel diffractive imager: a diffractive array 4 m large, with 696 Fresnel zones operating in the ultra-violet domain. The diffractive arrays are opaque foils punched with a large number of void subapertures with carefully designed shapes and positions. In the proposed space missions, these punched foils would be deployed in space. Depending on the size of the array and on the working spectral band, the focal length of such imagers will range from a few kilometers to a few tens of kilometers. Thus, such space mission requires a formation flying configuration for two satellites around the L2 Sun-Earth Lagragian point. In this article, we investigate numerically the potential of Fresnel arrays for imaging circumstellar dust environments. These simulations are based upon simple protostellar disk models, and on the computed optical characteristics of the instrument. The results show that protoplanetary disks at distances up to a few thousand parsecs can be successfully studied with a 4 m aperture Fresnel imager in the UV. 相似文献
20.
Alexander Hubbard Mordecai-Mark Mac Low Denton S. Ebel 《Meteoritics & planetary science》2018,53(7):1507-1515
Meteoritical and astrophysical models of planet formation make contradictory predictions for dust concentration factors in chondrule-forming regions of the solar nebula. Meteoritical and cosmochemical models strongly suggest that chondrules, a key component of the meteoritical record, formed in regions with solids-to-gas mass ratios orders above the solar nebula average. However, models of dust grain dynamics in protoplanetary disks struggle to surpass concentration factors of a few except during very short-lived stages in a dust grain's life. Worse, those models do not predict significant concentration factors for dust grains the size of chondrule precursors. We briefly develop the difficulty in concentrating dust particles in the context of nebular chondrule formation and show that the disagreement is sufficiently stark that cosmochemists should explore ideas that might revise the concentration factor requirements downward. 相似文献