scholarly journals Heavy-metal Jupiters by major mergers: metallicity versus mass for giant planets

2020 ◽  
Vol 498 (1) ◽  
pp. 680-688 ◽  
Author(s):  
Sivan Ginzburg ◽  
Eugene Chiang
Keyword(s):  
Heavy Metal ◽  
Accretion Rate ◽  
Giant Planet ◽  
Giant Planets ◽  
Solid Core ◽  
Core Mass ◽  
The Core ◽  
Multiple Cores ◽  
Merger Rate ◽  
Gas Accretion

ABSTRACT Some Jupiter-mass exoplanets contain ${\sim}100\, {\rm M}_{\hbox{$\oplus $}}$ of metals, well above the ${\sim}10\, {\rm M}_{\hbox{$\oplus $}}$ typically needed in a solid core to trigger giant planet formation by runaway gas accretion. We demonstrate that such ‘heavy-metal Jupiters’ can result from planetary mergers near ∼10 au. Multiple cores accreting gas at runaway rates gravitationally perturb one another on to crossing orbits such that the average merger rate equals the gas accretion rate. Concurrent mergers and gas accretion implies the core mass scales with the total planet mass as Mcore ∝ M1/5 – heavier planets harbour heavier cores, in agreement with the observed relation between total mass and metal mass. While the average gas giant merges about once to double its core, others may merge multiple times, as merger trees grow chaotically. We show that the dispersion of outcomes inherent in mergers can reproduce the large scatter in observed planet metallicities, assuming $3{-}30\, {\rm M}_{\hbox{$\oplus $}}$ pre-runaway cores. Mergers potentially correlate metallicity, eccentricity, and spin.

scholarly journals Adapting a solid accretion scenario for migrating planets in fargo3d

2019 ◽  
Vol 490 (2) ◽  
pp. 2336-2346
Author(s):  
L A DePaula ◽  
T A Michtchenko ◽  
P A Sousa-Silva
Keyword(s):  
Time Scale ◽  
Accretion Rate ◽  
Critical Mass ◽  
Numerical Approach ◽  
Solid Core ◽  
Planetary Formation ◽  
Stellar Envelope ◽  
The Core ◽  
Planetary Migration ◽  
Gas Accretion

ABSTRACT In this work, we adapt a module for planetary formation within the hydrodynamic code fargo3d. Planetary formation is modelled by a solid core accretion scenario, with the core growing in oligarchic regime. The initial superficial density of planetesimals is proportional to the initial superficial density of gas in the disc. We include a numerical approach to describe the evolution of the eccentricity and the inclination of planetesimals during the formation. This approach impacts directly on the accretion rate of solids. When the core reaches a critical mass, gas accretion begins, following the original fargo scheme adapted to the fargo3d code. To exemplify how the module for planetary formation can be used, we investigate the migration of a planet in a 2D, locally isothermal gas disc with a prescribed accretion rate, analysing the time-scale involved in the planetary migration process along with the time-scale for planetary formation. The analysis reveals that the mass of the nucleus must be close to its critical value when crossing the ice line to avoid the planet’s fall into the stellar envelope. This will allow enough time for the planet to initiate runaway gas accretion, leading to a rapid mass increase and entering type II planetary migration.

scholarly journals Self-gravitating planetary envelopes and the core-nucleated instability

2019 ◽  
Vol 490 (3) ◽  
pp. 3144-3157 ◽  
Author(s):  
William Béthune
Keyword(s):  
Planet Formation ◽  
Three Dimensions ◽  
High Mass ◽  
Solid Core ◽  
Core Mass ◽  
Hydrodynamic Simulations ◽  
One Dimensional ◽  
Linear Evolution ◽  
The Core ◽  
Gas Accretion

Abstract Planet formation scenarios can be constrained by the ratio of the gaseous envelope mass relative to the solid core mass in the observed exoplanet populations. One-dimensional calculations find a critical (maximal) core mass for quasi-static envelopes to exist, suggesting that envelopes around more massive cores should collapse due to a ‘core-nucleated’ instability. We study self-gravitating planetary envelopes via hydrodynamic simulations, progressively increasing the dimensionality of the problem. We characterize the core-nucleated instability and its non-linear evolution into runaway gas accretion in one-dimensional spherical envelopes. We show that rotationally supported envelopes can enter a runaway accretion regime via polar shocks in a two-dimensional axisymmetric model. This picture remains valid for high-mass cores in three dimensions, where the gas gravity mainly adds up to the core gravity and enhances the mass accretion rate of the planet in time. We relate the core-nucleated instability to the absence of equilibrium connecting the planet to its parent disc and discuss its relevance for massive planet formation.

scholarly journals Formation of the Giant Planets

1981 ◽  
Vol 93 ◽  
pp. 133-134
Author(s):  
Hiroshi Mizuno
Keyword(s):  
Radiative Transfer ◽  
Solar Nebula ◽  
Giant Planet ◽  
Giant Planets ◽  
Core Mass ◽  
The Core ◽  
Gaseous Envelope

The structure of a gaseous envelope surrounding a icy/rocky core is studied in consideration of radiative transfer. It is found that when the core grows beyond a critical core mass, the envelope cannot be in equilibrium and collapses onto the core to form a proto-giant planet. The results are as follows (for details, see Mizuno 1980).1) The critical core mass is smaller than that estimated by Perri and Cameron (1974) and Mizuno, Nakazawa and Hayashi (1978). 2) When the grain opacity in the envelope varies from 0 to 1 cm2/g, the critical core mass changes from ~2 to ~12 Earth's masses. 3) The critical core mass is independent of the region in the solar nebula.These are due to the existence of the radiative region in the envelope.

scholarly journals The fate of planetary cores in giant and ice-giant planets

2019 ◽  
Vol 631 ◽  
pp. L4 ◽  
Author(s):  
S. Mazevet ◽  
R. Musella ◽  
F. Guyot
Keyword(s):  
High Pressure ◽  
Ab Initio ◽  
Inner Core ◽  
Giant Planets ◽  
Ab Initio Molecular Dynamics ◽  
Solid Core ◽  
Potential Core ◽  
Melting Temperatures ◽  
The Core ◽  
Pressure Melting

Context. The Juno probe that currently orbits Jupiter measures its gravitational moments with great accuracy. Preliminary results suggest that the core of the planet may be eroded. While great attention has been paid to the material properties of elements constituting the envelope, little is known about those that constitute the core. This situation clutters our interpretation the Juno data and modeling of giant planets and exoplanets in general. Aims. We calculate the high-pressure melting temperatures of three potential components of the cores of giant planets, water, iron, and a simple silicate, MgSiO3, to investigate the state of the deep inner core. Methods. We used ab initio molecular dynamics simulations to calculate the high-pressure melting temperatures of the three potential core components. The planetary adiabats were obtained by solving the hydrostatic equations in a three-layer model adjusted to reproduce the measured gravitational moments. Recently developed ab initio equations of state were used for the envelope and the core. Results. We find that the cores of the giant and ice-giant planets of the solar system differ because the pressure–temperature conditions encountered in each object correspond to different regions of the phase diagrams. For Jupiter and Saturn, the results are compatible with a diffuse core and mixing of a significant fraction of metallic elements in the envelope, leading to a convective and/or a double-diffusion regime. We also find that their solid cores vary in nature and size throughout the lifetimes of these planets. The solid cores of the two giant planets are not primordial and nucleate and grow as the planets cool. We estimate that the solid core of Jupiter is 3 Gyr old and that of Saturn is 1.5 Gyr old. The situation is less extreme for Uranus and Neptune, whose cores are only partially melted. Conclusions. To model Jupiter, the time evolution of the interior structure of the giant planets and exoplanets in general, their luminosity, and the evolution of the tidal effects over their lifetimes, the core should be considered as crystallizing and growing rather than gradually mixing into the envelope due to the solubility of its components.

scholarly journals Dynamical stability of giant planets: the critical adiabatic index in the presence of a solid core

2021 ◽  
Vol 507 (4) ◽  
pp. 6215-6224
Author(s):  
Suman Kumar Kundu ◽  
Eric R Coughlin ◽  
Andrew N Youdin ◽  
Philip J Armitage
Keyword(s):  
Incompressible Fluid ◽  
Giant Planets ◽  
Adiabatic Index ◽  
Dynamical Instability ◽  
Solid Core ◽  
Dominant Effect ◽  
Instability Strip ◽  
The Core ◽  
Core Accretion ◽  
Upper Boundary

ABSTRACT The dissociation and ionization of hydrogen, during the formation of giant planets via core accretion, reduce the effective adiabatic index γ of the gas and could trigger dynamical instability. We generalize the analysis of Chandrasekhar, who determined that the threshold for instability of a self-gravitating hydrostatic body lies at γ = 4/3, to account for the presence of a planetary core, which we model as an incompressible fluid. We show that the dominant effect of the core is to stabilize the envelope to radial perturbations, in some cases completely (i.e. for all γ > 1). When instability is possible, unstable planetary configurations occupy a strip of γ values whose upper boundary falls below γ = 4/3. Fiducial evolutionary tracks of giant planets forming through core accretion appear unlikely to cross the dynamical instability strip that we define.

scholarly journals On Early Evolution of Accreting Stars

1987 ◽  
Vol 115 ◽  
pp. 440-441
Author(s):  
B. M. Shustov ◽  
A. V. Tutukov
Keyword(s):  
Accretion Rate ◽  
Life Time ◽  
Early Evolution ◽  
Dominant Factor ◽  
Spherically Symmetric ◽  
Core Mass ◽  
The Core ◽  
Pass Through ◽  
The Moment ◽  
First Time

Accretion is a dominant factor in the early evolution of stars. The first time an accretion regime settles in is when a dusty opaque core forms. The mass of adiabatically contracting core inside the isothermally collapsing envelope depends only on the optical properties of dust. Spherically symmetric models of dusty cores were constructed using the Henyey technique with accretion boundary conditions (Menshchikov 1986). It appears that all protostars with normal chemical composition should pass through the stage of a quasistatic dusty core. The evolution of dusty cores is similar to that of “normal” young stars with accretion. One could distinguish convective, radiative and central core contraction phases. The life-time tc of the core depends on the core mass Mc and the accretion rate Ṁ (for Mc = 0.01 M⊙ and Ṁ = 1.6x10−6, 1.6x10−5 M⊙/year tc = 1.2x104, 3x103 yrs consequently). After dust exhaustion in the core it collapses and a central ionized quasistatic region grows in several tens of years. A flash of infrared radiation at the moment is not excluded.

scholarly journals Composition of massive giant planets

2010 ◽  
Vol 6 (S276) ◽  
pp. 95-100
Author(s):  
Ravit Helled ◽  
Peter Bodenheimer ◽  
Jack J. Lissauer
Keyword(s):  
Large Range ◽  
Giant Planet ◽  
Giant Planets ◽  
Heavy Elements ◽  
Formation Model ◽  
The Core ◽  
Accretion Model ◽  
Low Mass ◽  
Core Accretion ◽  
Host Stars

AbstractThe two current models for giant planet formation are core accretion and disk instability. We discuss the core masses and overall planetary enrichment in heavy elements predicted by the two formation models, and show that both models could lead to a large range of final compositions. For example, both can form giant planets with nearly stellar compositions. However, low-mass giant planets, enriched in heavy elements compared to their host stars, are more easily explained by the core accretion model. The final structure of the planets, i.e., the distribution of heavy elements, is not firmly constrained in either formation model.

Constraining planetary interiors with the Love number k2

2010 ◽  
Vol 6 (S276) ◽  
pp. 482-484
Author(s):  
Ulrike Kramm ◽  
Nadine Nettelmann ◽  
Ronald Redmer
Keyword(s):  
Density Distribution ◽  
Extrasolar Planets ◽  
Giant Planets ◽  
Love Number ◽  
Core Mass ◽  
Planetary Interiors ◽  
Orbital Parameters ◽  
First Order ◽  
The Core ◽  
Observable Parameter

AbstractFor the solar sytem giant planets the measurement of the gravitational moments J2 and J4 provided valuable information about the interior structure. However, for extrasolar planets the gravitational moments are not accessible. Nevertheless, an additional constraint for extrasolar planets can be obtained from the tidal Love number k2, which, to first order, is equivalent to J2. k2 quantifies the quadrupolic gravity field deformation at the surface of the planet in response to an external perturbing body and depends solely on the planet's internal density distribution. On the other hand, the inverse deduction of the density distribution of the planet from k2 is non-unique. The Love number k2 is a potentially observable parameter that can be obtained from tidally induced apsidal precession of close-in planets (Ragozzine & Wolf 2009) or from the orbital parameters of specific two-planet systems in apsidal alignment (Mardling 2007). We find that for a given k2, a precise value for the core mass cannot be derived. However, a maximum core mass can be inferred which equals the core mass predicted by homogeneous zero metallicity envelope models. Using the example of the extrasolar transiting planet HAT-P-13b we show to what extend planetary models can be constrained by taking into account the tidal Love number k2.

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