scholarly journals The Story of Planets: Anchoring Numerics in Reality

2013 ◽  
Vol 8 (S299) ◽  
pp. 123-130
Author(s):  
Zoë M. Leinhardt
Keyword(s):  
Numerical Simulations ◽  
Extrasolar Planets ◽  
Planet Formation ◽  
Planetary System ◽  
Numerical Models ◽  
Building Blocks ◽  
Solar Mass ◽  
Hot Jupiters ◽  
Planetary Cores ◽  
Low Mass

AbstractBuilding a complete coherent model of planet formation has proven difficult. There are gaps in the observational record, difficult physical processes that we have yet to fully understand, such as planetesimal formation, and an extensive list of observationally determined constraints that the model must fulfil. For example, the diversity of extrasolar planets detected to date is staggering – from single hot-Jupiters to multiple planet systems with several tightly packed super-Earths. In addition, the characteristics of the host stars are broad from single solar-mass stars to tight binaries and low mass, low metalicity stars. Even more surprising, perhaps, is the frequency of detection and thus, the implied efficiency of the planet formation process. Any theoretical model must not just be able to explain how planets form but must also explain the frequency and diversity of planetary systems. So why is planet formation so prolific? What parameters determine the type of planetary system that will result? How important are the initial parameters of the protoplanetary disk, such as composition, versus stochastic effects, such as gravitational scattering events, that occur during the evolution of the planetary system?Current observations of extrasolar planets provide snapshots in time of the earliest and latest stages of planet formation but do not show the evolution between the two. It is at this point that we must rely on numerical models to evolve proto-planetary disks into planets. But how can we validate the results of our numerical simulations if the middle stages of planet formation are effectively invisible? Collisions are a core component of planet formation. Planetesimals, the building blocks of planets, collide with one another as they grow and evolve into planets or planetary cores and are viscously stirred by larger protoplanets and fully-formed planets. The range of impact parameters encountered during growth from planetesimals to planets span multiple collision outcome regimes: cratering, merging, disruption, and hit-and-run events. Most of these collisions produce significant debris and dust. If we have a good understanding of the production of collisional debris we can use it as an indirect tracer of on-going planetary evolution even if the planets themselves are not directly detectable.In this paper I will show how numerical simulations of planet formation including realistic collision modelling can be used to predict, and be constrained by, observations.

scholarly journals Pebble accretion in self-gravitating protostellar discs

2019 ◽  
Vol 485 (4) ◽  
pp. 4465-4473
Author(s):  
D H Forgan
Keyword(s):  
Time Scales ◽  
Planet Formation ◽  
Density Ratio ◽  
Streaming Instability ◽  
Planetary Cores ◽  
Low Mass ◽  
Spiral Structures ◽  
Protostellar Discs ◽  
Core Accretion ◽  
Solid Bodies

Abstract Pebble accretion has become a popular component to core accretion models of planet formation, and is especially relevant to the formation of compact, resonant terrestrial planetary systems. Pebbles initially form in the inner protoplanetary disc, sweeping outwards in a radially expanding front, potentially forming planetesimals and planetary cores via migration and the streaming instability. This pebble front appears at early times, in what is typically assumed to be a low-mass disc. We argue this picture is in conflict with the reality of young circumstellar discs, which are massive and self-gravitating. We apply standard pebble accretion and streaming instability formulae to self-gravitating protostellar disc models. Fragments will open a gap in the pebble disc, but they will likely fail to open a gap in the gas, and continue rapid inward migration. If this does not strongly perturb the pebble disc, our results show that disc fragments will accrete pebbles efficiently. We find that in general the pebble-to-gas-density ratio fails to exceed 0.01, suggesting that the streaming instability will struggle to operate. It may be possible to activate the instability if 10 cm grains are available, and spiral structures can effectively concentrate them in regions of low gravito-turbulence. If this occurs, lunar mass cores might be assembled on time-scales of a few thousand years, but this is likely to be rare, and is far from proven. In any case, this work highlights the need for study of how self-gravitating protostellar discs define the distribution and properties of solid bodies, for future planet formation by core accretion.

scholarly journals Models of very-low-mass stars, brown dwarfs and exoplanets

2012 ◽  
Vol 370 (1968) ◽  
pp. 2765-2777 ◽  
Author(s):  
F. Allard ◽  
D. Homeier ◽  
B. Freytag
Keyword(s):  
Extrasolar Planets ◽  
Cloud Model ◽  
Brown Dwarfs ◽  
Spectroscopic Properties ◽  
Model Atmosphere ◽  
Low Mass Stars ◽  
Hot Jupiters ◽  
Solar Type ◽  
Low Mass ◽  
First Time

Within the next few years, GAIA and several instruments aiming to image extrasolar planets will be ready. In parallel, low-mass planets are being sought around red dwarfs, which offer more favourable conditions, for both radial velocity detection and transit studies, than solar-type stars. In this paper, the authors of a model atmosphere code that has allowed the detection of water vapour in the atmosphere of hot Jupiters review recent advances in modelling the stellar to substellar transition. The revised solar oxygen abundances and cloud model allow the photometric and spectroscopic properties of this transition to be reproduced for the first time. Also presented are highlight results of a model atmosphere grid for stars, brown dwarfs and extrasolar planets.

scholarly journals Towards the characterization of the hot Neptune/super-Earth population around nearby bright stars

2008 ◽  
Vol 4 (S253) ◽  
pp. 502-505 ◽  
Author(s):  
C. Lovis ◽  
M. Mayor ◽  
F. Bouchy ◽  
F. Pepe ◽  
D. Queloz ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Extrasolar Planets ◽  
Large Population ◽  
Long Term Stability ◽  
Data Points ◽  
Solar Type ◽  
Low Mass ◽  
Orbital Periods

AbstractThe HARPS search for low-mass extrasolar planets has been ongoing for more than 4 years, targeting originally about 400 bright FGK dwarfs in the solar neighbourhood. The published low-mass planetary systems coming from this survey are fully confirmed by subsequent observations, which demonstrate the sub-m/s long-term stability reached by HARPS. The complex RV curves of these systems have led us to focus on a smaller sample of stars, accumulating more data points per star. We perform a global search in our data to assess the existence of the large population of ice giants and super-Earths predicted by numerical simulations of planet formation. We indeed detect about 45 candidates having minimum masses below 30 M⊕ and orbital periods below 50 days. These numbers are preliminary since the existence of these objects has to be confirmed by subsequent observations. However, they indicate that about 30% of solar-type stars may have such close-in, low-mass planets. Some emerging properties of this low-mass population are presented. We finally discuss the prospects for finding transiting objects among these candidates, which may possibly yield the first nearby, transiting super-Earth.

scholarly journals System-level fractionation of carbon from disk and planetesimal processing 

2021 ◽  
Author(s):  
Tim Lichtenberg ◽  
Sebastiaan Krijt
Keyword(s):  
Planetary System ◽  
Numerical Models ◽  
Planetary Systems ◽  
Building Blocks ◽  
Environmental Context ◽  
System Level ◽  
Circumstellar Disk ◽  
Internal Heating ◽  
Compositional Evolution ◽  
Total Budget

<div class="page" title="Page 1"> <div class="section"> <div class="layoutArea"> <div class="column"> <p>Finding and characterizing extrasolar Earth analogs will rely on interpretation of the planetary system’s environmental context. The total budget and fractionation between C–H–O species sensitively affect the climatic and geodynamic state of terrestrial worlds, but their main delivery channels are poorly constrained. We connect numerical models of volatile chemistry and pebble coagulation in the circumstellar disk with the internal compositional evolution of planetesimals during the primary accretion phase. Our simulations demonstrate that disk chemistry and degassing from planetesimals operate on comparable timescales and can fractionate the relative abundances of major water and carbon carriers by orders of magnitude. As a result, individual planetary systems with significant planetesimal processing display increased correlation in the volatile budget of planetary building blocks relative to no internal heating. Planetesimal processing in a subset of systems increases the variance of volatile contents across planetary systems. Our simulations thus suggest that exoplanetary atmospheric compositions may provide constraints on <em>when</em> a specific planet formed.</p> </div> </div> </div> </div>

scholarly journals Bifurcation of planetary building blocks during Solar System formation

Science ◽  
2021 ◽  
Vol 371 (6527) ◽  
pp. 365-370
Author(s):  
Tim Lichtenberg ◽  
Joanna Dra̧żkowska ◽  
Maria Schönbächler ◽  
Gregor J. Golabek ◽  
Thomas O. Hands
Keyword(s):  
Solar System ◽  
Planet Formation ◽  
Numerical Models ◽  
Building Blocks ◽  
Protoplanetary Disk ◽  
Outer Solar System ◽  
Solar System Formation ◽  
Source Regions ◽  
Mass Divergence ◽  
Internal Evolution

Geochemical and astronomical evidence demonstrates that planet formation occurred in two spatially and temporally separated reservoirs. The origin of this dichotomy is unknown. We use numerical models to investigate how the evolution of the solar protoplanetary disk influenced the timing of protoplanet formation and their internal evolution. Migration of the water snow line can generate two distinct bursts of planetesimal formation that sample different source regions. These reservoirs evolve in divergent geophysical modes and develop distinct volatile contents, consistent with constraints from accretion chronology, thermochemistry, and the mass divergence of inner and outer Solar System. Our simulations suggest that the compositional fractionation and isotopic dichotomy of the Solar System was initiated by the interplay between disk dynamics, heterogeneous accretion, and internal evolution of forming protoplanets.

scholarly journals Protostellar Disks, Planet Traps, and the Origins of Exoplanetary Systems

2013 ◽  
Vol 8 (S299) ◽  
pp. 365-369
Author(s):  
Ralph E. Pudritz ◽  
Yasuhiro Hasegawa
Keyword(s):  
Dead Zone ◽  
Semimajor Axis ◽  
Thermal Gradients ◽  
Hot Jupiters ◽  
Exoplanetary Systems ◽  
Planetary Cores ◽  
Accretion Rates ◽  
Disk Evolution ◽  
Low Mass ◽  
Jovian Planets

AbstractThe mass-semimajor axis diagram for exoplanets is populated by at least three distinct planetary populations: hot Jupiters at small orbital radii, more massive Jovian planets gathered at about 1 AU, and a rapidly growing population of SuperEarths at short periods. Our work shows that low mass and rapidly migrating planetary cores get trapped at disk inhomogeneities, where strong density or thermal gradients exist (namely dead zone boundaries, ice lines, and disk heating transition regions). Planet growth and movement occur at rates dictated by planetary accretion, and the slow radial inward motion of the traps due to falling disk accretion rates during disk evolution. By combining the theory of traps in evolving disks with standard ideas about how protoplanets accrete, we develop evolutionary tracks of how planets evolve in the mass- semimajor axis diagram. Our models account for the planetary “pile-up” at 1AU, the origin of SuperEarths and hot Jupiters, and the relative scarcity of Jovian planets at large distances.

scholarly journals Earth-size planet formation in the habitable zone of circumbinary stars

2020 ◽  
Vol 494 (1) ◽  
pp. 1045-1057 ◽  
Author(s):  
G O Barbosa ◽  
O C Winter ◽  
A Amarante ◽  
A Izidoro ◽  
R C Domingos ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Planet Formation ◽  
Terrestrial Planet ◽  
Close Binary ◽  
Habitable Zone ◽  
Density Profiles ◽  
Habitable Planets ◽  
Habitable Zones ◽  
Test Particles ◽  
The Stability

ABSTRACT This work investigates the possibility of close binary (CB) star systems having Earth-size planets within their habitable zones (HZs). First, we selected all known CB systems with confirmed planets (totaling 22 systems) to calculate the boundaries of their respective HZs. However, only eight systems had all the data necessary for the computation of HZ. Then, we numerically explored the stability within HZs for each one of the eight systems using test particles. From the results, we selected five systems that have stable regions inside HZs, namely Kepler-34,35,38,413, and 453. For these five cases of systems with stable regions in HZ, we perform a series of numerical simulations for planet formation considering discs composed of planetary embryos and planetesimals, with two distinct density profiles, in addition to the stars and host planets of each system. We found that in the case of the Kepler-34 and 453 systems, no Earth-size planet is formed within HZs. Although planets with Earth-like masses were formed in Kepler-453, they were outside HZ. In contrast, for the Kepler-35 and 38 systems, the results showed that potentially habitable planets are formed in all simulations. In the case of the Kepler-413system, in just one simulation, a terrestrial planet was formed within HZ.

scholarly journals Composition of Ices in Low‐Mass Extrasolar Planets

2008 ◽  
Vol 681 (2) ◽  
pp. 1624-1630 ◽  
Author(s):  
U. Marboeuf ◽  
O. Mousis ◽  
D. Ehrenreich ◽  
Y. Alibert ◽  
A. Cassan ◽  
...  
Keyword(s):  
Extrasolar Planets ◽  
Low Mass

Vortex-Induced Vibrations of a Cylinder at Subcritical Reynolds Number

2011 ◽  
Author(s):  
Yoann Jus ◽  
Elisabeth Longatte ◽  
Jean-Camille Chassaing ◽  
Pierre Sagaut
Keyword(s):  
Reynolds Number ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Damping Ratio ◽  
Experimental Studies ◽  
Cross Flow ◽  
Physical Analysis ◽  
Arbitrary Lagrangian Eulerian ◽  
Vortex Induced Vibrations ◽  
Low Mass

The present work focusses on the numerical study of Vortex-Induced Vibrations (VIV) of an elastically mounted cylinder in a cross flow at moderate Reynolds numbers. Low mass-damping experimental studies show that the dynamic behavior of the cylinder exhibits a three-branch response model, depending on the range of the reduced velocity. However, few numerical simulations deal with accurate computations of the VIV amplitudes at the lock-in upper branch of the bifurcation diagram. In this work, the dynamic response of the cylinder is investigated by means of three-dimensional Large Eddy Simulation (LES). An Arbitrary Lagrangian Eulerian framework is employed to account for fluid solid interface boundary motion and grid deformation. Numerous numerical simulations are performed at a Reynolds number of 3900 for both no damping and low-mass damping ratio and various reduced velocities. A detailed physical analysis is conducted to show how the present methodology is able to capture the different VIV responses.

scholarly journals A Decreased Probability of Habitable Planet Formation around Low‐Mass Stars

2007 ◽  
Vol 669 (1) ◽  
pp. 606-614 ◽  
Author(s):  
Sean N. Raymond ◽  
John Scalo ◽  
Victoria S. Meadows
Keyword(s):  
Planet Formation ◽  
Low Mass Stars ◽  
Low Mass ◽  
Habitable Planet
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