scholarly journals Close-in giant-planet formation via in-situ gas accretion and their natal disk properties

2019 ◽  
Vol 629 ◽  
pp. L1
Author(s):  
Yasuhiro Hasegawa ◽  
Tze Yeung Mathew Yu ◽  
Bradley M. S. Hansen
Keyword(s):  
Large Scale ◽  
Solar Nebula ◽  
Giant Planet ◽  
Central Star ◽  
Giant Planets ◽  
Occurrence Rate ◽  
Minimum Mass ◽  
Gas Accretion ◽  
Increasing Function

Aims. The origin of close-in Jovian planets is still elusive. We examine the in-situ gas accretion scenario as a formation mechanism of these planets. Methods. We reconstruct natal disk properties from the occurrence rate distribution of close-in giant planets, under the assumption that the occurrence rate may reflect the gas accretion efficiency onto cores of these planets. Results. We find that the resulting gas surface density profile becomes an increasing function of the distance from the central star with some structure at r ≃ 0.1 au. This profile is quite different from the standard minimum-mass solar nebula model, while our profile leads to better reproduction of the population of observed close-in super-Earths based on previous studies. We compute the resulting magnetic field profiles and find that our profiles can be fitted by stellar dipole fields (∝r−3) in the vicinity of the central star and large-scale fields (∝r−2) at the inner disk regions, either if the isothermal assumption breaks down or if nonideal magnetohydrodynamic effects become important. For both cases, the transition between these two profiles occurs at r ≃ 0.1 au, which corresponds to the period valley of giant exoplanets. Conclusions. Our work provides an opportunity to test the in-situ gas accretion scenario against disk quantities, which may constrain the gas distribution of the minimum-mass extrasolar nebula.

scholarly journals Rapid Formation of Gas-giant Planets via Collisional Coagulation from Dust Grains to Planetary Cores

2021 ◽  
Vol 922 (1) ◽  
pp. 16
Author(s):  
Hiroshi Kobayashi ◽  
Hidekazu Tanaka
Keyword(s):  
Protoplanetary Disks ◽  
Central Star ◽  
Giant Planets ◽  
Solar Systems ◽  
Evolution Path ◽  
Planetary Cores ◽  
Rapid Formation ◽  
Gas Giant ◽  
Planetary Migration ◽  
Gas Accretion

Abstract Gas-giant planets, such as Jupiter, Saturn, and massive exoplanets, were formed via the gas accretion onto the solid cores, each with a mass of roughly 10 Earth masses. However, rapid radial migration due to disk–planet interaction prevents the formation of such massive cores via planetesimal accretion. Comparably rapid core growth via pebble accretion requires very massive protoplanetary disks because most pebbles fall into the central star. Although planetesimal formation, planetary migration, and gas-giant core formation have been studied with a lot of effort, the full evolution path from dust to planets is still uncertain. Here we report the result of full simulations for collisional evolution from dust to planets in a whole disk. Dust growth with realistic porosity allows the formation of icy planetesimals in the inner disk (≲10 au), while pebbles formed in the outer disk drift to the inner disk and there grow to planetesimals. The growth of those pebbles to planetesimals suppresses their radial drift and supplies small planetesimals sustainably in the vicinity of cores. This enables rapid formation of sufficiently massive planetary cores within 0.2–0.4 million years, prior to the planetary migration. Our models shows the first gas giants form at 2–7 au in rather common protoplanetary disks, in agreement with the exoplanet and solar systems.

scholarly journals 1. The Origin of Comets

1977 ◽  
Vol 39 ◽  
pp. 453-467 ◽  
Author(s):  
A. H. Delsemme
Keyword(s):  
Solar System ◽  
Mass Loss ◽  
Empirical Evidence ◽  
Empirical Data ◽  
Solar Nebula ◽  
Giant Planets ◽  
Outer Ring ◽  
Arrow Of Time ◽  
Satisfactory Theory

Empirical data are confronted with different hypotheses on the origin of comets. The hypotheses are classified into three categories: 1) Comets were condensed from the solar nebula and ejected later into the Oort’s cloud. 2) Comets were condensed in situ, more or less recently, on their present trajectories; 3) Reversing the arrow of time in the traditional evolution of comets. Only two hypotheses, both from the first category, are found to be in agreement with all empirical data. The first hypothesis explains the origin of the Oort’s cloud by the perturbations of the giant planets (mainly Uranus and Neptune and possibly Pluto) on a ring of proto-comets, during the final accretion stages of the solar system. The second hypothesis uses the fast mass loss of the solar nebula to expell an outer ring of proto-comets into elliptic trajectories. Although no empirical evidence requests that the Oort’s cloud be older than a few million years, its matter is not likely to be from a different reservoir than solar system stuff, and no satisfactory theory explains its formation more recently than 4,5 billion years ago.

scholarly journals Possible in situ Formation of Close Giant Planets in a Passive Quiescent Nebula

2004 ◽  
Vol 202 ◽  
pp. 285-290
Author(s):  
Yoshitsugu Nakagawa
Keyword(s):  
Standard Model ◽  
Giant Planet ◽  
Giant Planets ◽  
Protoplanetary Nebulae ◽  
The Standard Model ◽  
In Situ Formation ◽  
Innermost Region

Formation of giant planets along the standard model is considered in the innermost region of protoplanetary nebulae where turbulence has already decayed. Preference of quiescent nebulae is discussed. It is shown that if dust material enough to form a core with about ten times Earth mass and the corresponding amount of gas exist in the innermost region, a giant planet with mass somewhat larger than our Jupiter can form there.

scholarly journals Constraining Planetary Migration Mechanisms in Systems of Giant Planets

2013 ◽  
Vol 8 (S299) ◽  
pp. 386-390
Author(s):  
Rebekah I. Dawson ◽  
Ruth A. Murray-Clay ◽  
John Asher Johnson
Keyword(s):  
Giant Planet ◽  
Giant Planets ◽  
Tidal Dissipation ◽  
Hot Jupiters ◽  
Short Period ◽  
Pile Up ◽  
Planetary Migration ◽  
Multi Body ◽  
Host Stars

AbstractIt was once widely believed that planets formed peacefully in situ in their proto-planetary disks and subsequently remain in place. Instead, growing evidence suggests that many giant planets undergo dynamical rearrangement that results in planets migrating inward in the disk, far from their birthplaces. However, it remains debated whether this migration is caused by smooth planet-disk interactions or violent multi-body interactions. Both classes of model can produce Jupiter-mass planets orbiting within 0.1 AU of their host stars, also known as hot Jupiters. In the latter class of model, another planet or star in the system perturbs the Jupiter onto a highly eccentric orbit, which tidal dissipation subsequently shrinks and circularizes during close passages to the star. We assess the prevalence of smooth vs. violent migration through two studies. First, motivated by the predictions of Socrates et al. (2012), we search for super-eccentric hot Jupiter progenitors by using the “photoeccentric effect” to measure the eccentricities of Kepler giant planet candidates from their transit light curves. We find a significant lack of super- eccentric proto-hot Jupiters compared to the number expected, allowing us to place an upper limit on the fraction of hot Jupiters created by stellar binaries. Second, if both planet-disk and multi-body interactions commonly cause giant planet migration, physical properties of the proto-planetary environment may determine which is triggered. We identify three trends in which giant planets orbiting metal rich stars show signatures of planet-planet interactions: (1) gas giants orbiting within 1 AU of metal-rich stars have a range of eccentricities, whereas those orbiting metal- poor stars are restricted to lower eccentricities; (2) metal-rich stars host most eccentric proto-hot Jupiters undergoing tidal circularization; and (3) the pile-up of short-period giant planets, missing in the Kepler sample, is a feature of metal-rich stars and is largely recovered for giants orbiting metal-rich Kepler host stars. These two studies suggest that both disk migration and planet-planet interactions may be widespread, with the latter occurring primarily in metal-rich planetary systems where multiple giant planets can form. Funded by NSF-GRFP DGE-1144152.

scholarly journals Enhanced Lidov–Kozai migration and the formation of the transiting giant planet WD 1856+534 b

2020 ◽  
Vol 501 (1) ◽  
pp. 507-514 ◽  
Author(s):  
Christopher E O’Connor ◽  
Bin Liu ◽  
Dong Lai
Keyword(s):  
Main Sequence ◽  
Semimajor Axis ◽  
Giant Planet ◽  
Giant Planets ◽  
Occurrence Rate ◽  
M Dwarfs ◽  
High Eccentricity ◽  
Absolute Limit ◽  
Short Period ◽  
Wide Range

ABSTRACT We investigate the possible origin of the transiting giant planet WD 1856+534 b, the first strong exoplanet candidate orbiting a white dwarf, through high-eccentricity migration (HEM) driven by the Lidov–Kozai (LK) effect. The host system’s overall architecture is a hierarchical quadruple in the ‘2 + 2’ configuration, owing to the presence of a tertiary companion system of two M-dwarfs. We show that a secular inclination resonance in 2 + 2 systems can significantly broaden the LK window for extreme eccentricity excitation (e ≳ 0.999), allowing the giant planet to migrate for a wide range of initial orbital inclinations. Octupole effects can also contribute to the broadening of this ‘extreme’ LK window. By requiring that perturbations from the companion stars be able to overcome short-range forces and excite the planet’s eccentricity to e ≃ 1, we obtain an absolute limit of $a_{1} \gtrsim 8 \, \mathrm{au}\, (a_{3} / 1500 \, \mathrm{au})^{6/7}$ for the planet’s semimajor axis just before migration (where a3 is the semimajor axis of the ‘outer’ orbit). We suggest that, to achieve a wide LK window through the 2 + 2 resonance, WD 1856 b likely migrated from $30 \, \mathrm{au}\lesssim a_{1} \lesssim 60 \, \mathrm{au}$, corresponding to ∼10–$20 \, \mathrm{au}$ during the host’s main-sequence phase. We discuss possible difficulties of all flavours of HEM affecting the occurrence rate of short-period giant planets around white dwarfs.

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 New Clues to Reveal Origins of Hot- and Warm-Jupiter: Mutual Occurrence Rate of Hot Jupiter，Warm Jupiter and Cold Jupiter

2021 ◽  
Author(s):  
Xiangning Su ◽  
Hui Zhang ◽  
Jilin Zhou
Keyword(s):  
Effective Temperature ◽  
Giant Planets ◽  
Detection Methods ◽  
Occurrence Rate ◽  
Origin And Evolution ◽  
History Of ◽  
Stellar Properties ◽  
Insight Into ◽  
Hot Jupiter

Abstract Many works based on the correlations between the occurrence rate of various giant planets and stellar properties of their hosts have provided clues revealing planetary formation processes. However, few researches have focused on the mutual occurrence rate of different type of planets and their dependency upon the stellar properties, which may help to provide an insight into the dynamics evolution history of planetary systems. To investigate the mutual occurrence rates, first we define three types of giant planets, i.e. cold Jupiter(CJ), warm Jupiter(WJ) and hot Jupiter(HJ), according to their position normalized by the snow-line in the system, ap > asnow, 0:1asnow < ap ≤ asnow and ap ≤ 0:1asnow, respectively. Then, we derive their occurrence rates(ηHJ,ηwJ,ηcJ) considering completeness correction caused by different detection methods (RV and transit) and surveys (HARPS& CORALIE and Kepler). Finally, we investigate the correlation between the relative occurrence rates, i.e. ηcJ/ηwJ or ηwJ/ηHJ, and various stellar properties, e.g. stellar metallicity and effective temperature Teff . We find that ηWJ from RV and transit surveys show a similar increasing trend with the increasing stellar effective temperature when Teff ≤ 6100K. While ηcJ from RV samples is almost flat within Teff in (4600K;6100K], and ηHJ from transit samples is increasing with increasing stellar effective temperature within 3600K < Te f f < 7100K. Further more, we find that the mutual occurrence rate between CJ and WJ, i.e. ηcJ/ηwJ , shows a decreasing trend with the increasing stellar effective temperature. In contrary, the ratio ηwJ/ηHJ is reversely depends on the stellar effective temperature. After a series of consistency tests, our results suggest the in-situ hypothesis can be excluded from the formation process of both WJ and HJ. However, the origin and evolution history of HJ may be quite different from that of WJ.

scholarly journals The origin of the high metallicity of close-in giant exoplanets

2020 ◽  
Vol 633 ◽  
pp. A33 ◽  
Author(s):  
Sho Shibata ◽  
Ravit Helled ◽  
Masahiro Ikoma
Keyword(s):  
Giant Planet ◽  
Major Axis ◽  
Limited Range ◽  
Heavy Elements ◽  
Semi Major Axis ◽  
Dynamical Simulations ◽  
Gas Accretion ◽  
High Metallicity ◽  
Gas Drag

Context. Recent studies suggest that in comparison to their host star, many giant exoplanets are highly enriched with heavy elements and can contain several tens of Earth masses of heavy elements or more. Such enrichment is considered to have been delivered by the accretion of planetesimals in late formation stages. Previous dynamical simulations, however, have shown that planets cannot accrete such high masses of heavy elements through “in situ” planetesimal accretion. Aims. We investigate whether a giant planet migrating inward can capture planetesimals efficiently enough to significantly increase its metallicity. Methods. We performed orbital integrations of a migrating giant planet and planetesimals in a protoplanetary gas disc to infer the planetesimal mass that is accreted by the planet. Results. We find that the two shepherding processes of mean motion resonance trapping and aerodynamic gas drag inhibit the planetesimal capture of a migrating planet. However, the amplified libration allows the highly-excited planetesimals in the resonances to escape from the resonance trap and to be accreted by the planet. Consequently, we show that a migrating giant planet captures planetesimals with total mass of several tens of Earth masses if the planet forms at a few tens of AU in a relatively massive disc. We also find that planetesimal capture occurs efficiently in a limited range of semi-major axis and that the total captured planetesimal mass increases with increasing migration distances. Our results have important implications for understanding the relation between giant planet metallicity and mass, as we suggest that it reflects the formation location of the planet – or more precisely, the location where runaway gas accretion occurred. We also suggest the observed metal-rich close-in Jupiters migrated to their present locations from afar, where they had initially formed.

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