scholarly journals Exploring the conditions for forming cold gas giants through planetesimal accretion

2019 ◽  
Vol 631 ◽  
pp. A70 ◽  
Author(s):  
Anders Johansen ◽  
Bertram Bitsch
Keyword(s):  
Kuiper Belt ◽  
Oort Cloud ◽  
Asteroid Belt ◽  
Nominal Model ◽  
The Core ◽  
And Migration ◽  
The Masses ◽  
Core Accretion ◽  
Cold Gas ◽  
Protoplanetary Discs

The formation of cold gas giants similar to Jupiter and Saturn in orbit and mass is a great challenge for planetesimal-driven core accretion models because the core growth rates far from the star are low. Here we model the growth and migration of single protoplanets that accrete planetesimals and gas. We integrated the core growth rate using fits in the literature to N-body simulations, which provide the efficiency of accreting the planetesimals that a protoplanet migrates through. We take into account three constraints from the solar system and from protoplanetary discs: (1) the masses of the terrestrial planets and the comet reservoirs in Neptune’s scattered disc and the Oort cloud are consistent with a primordial planetesimal population of a few Earth masses per AU, (2) evidence from the asteroid belt and the Kuiper belt indicates that the characteristic planetesimal diameter is 100 km, and (3) observations of protoplanetary discs indicate that the dust is stirred by weak turbulence; this gas turbulence also excites the inclinations of planetesimals. Our nominal model built on these constraints results in maximum protoplanet masses of 0.1 Earth masses. Ignoring constraint (1) above, we show that even a planetesimal population of 1000 Earth masses, corresponding to 50 Earth masses per AU, fails to produce cold gas giants (although it successfully forms hot and warm gas giants). We conclude that a massive planetesimal reservoir is in itself insufficient to produce cold gas giants. The formation of cold gas giants by planetesimal accretion additionally requires that planetesimals are small and that the turbulent stirring is very weak, thereby violating all three above constraints.

scholarly journals Ceres’ partial differentiation: undifferentiated crust mixing with a water-rich mantle

2020 ◽  
Vol 633 ◽  
pp. A117 ◽  
Author(s):  
Wladimir Neumann ◽  
Ralf Jaumann ◽  
Julie Castillo-Rogez ◽  
Carol A. Raymond ◽  
Christopher T. Russell
Keyword(s):  
Thermal Evolution ◽  
Kuiper Belt ◽  
Radioactive Decay ◽  
Thermal Conditions ◽  
Asteroid Belt ◽  
Final Size ◽  
Water Ice ◽  
Modeled Structure ◽  
Internal States ◽  
And Migration

Aims. We model thermal evolution and water-rock differentiation of small ice-rock objects that accreted at different heliocentric distances, while also considering migration into the asteroid belt for Ceres. We investigate how water-rock separation and various cooling processes influence Ceres’ structure and its thermal conditions at present. We also draw conclusions about the presence of liquids and the possibility of cryovolcanism. Methods. We calculated energy balance in bodies heated by radioactive decay and compaction-driven water-rock separation in a three-component dust-water/ice-empty pores mixture, while also taking into consideration second-order processes, such as accretional heating, hydrothermal circulation, and ocean or ice convection. Calculations were performed for varying accretion duration, final size, surface temperature, and dust/ice ratio to survey the range of possible internal states for precursors of Ceres. Subsequently, the evolution of Ceres was considered in five sets of simulated models, covering different accretion and evolution orbits and dust/ice ratios. Results. We find that Ceres’ precursors in the inner solar system could have been both wet and dry, while in the Kuiper belt, they retain the bulk of their water content. For plausible accretion scenarios, a thick primordial crust may be retained over several Gyr, following a slow differentiation within a few hundreds of Myr, assuming an absence of destabilizing impacts. The resulting thermal conditions at present allow for various salt solutions at depths of ≲10 km. The warmest present subsurface is obtained for an accretion in the Kuiper belt and migration to the present orbit. Conclusions. Our results indicate that Ceres’ material could have been aqueously altered on small precursors. The modeled structure of Ceres suggests that a liquid layer could still be present between the crust and the core, which is consistent with Dawn observations and, thus, suggests accretion in the Kuiper belt. While the crust stability calculations indicate crust retention, the convection analysis and interior evolution imply that the crust could still be evolving.

scholarly journals GJ 273: on the formation, dynamical evolution, and habitability of a planetary system hosted by an M dwarf at 3.75 parsec

2020 ◽  
Vol 641 ◽  
pp. A23 ◽  
Author(s):  
Francisco J. Pozuelos ◽  
Juan C. Suárez ◽  
Gonzalo C. de Elía ◽  
Zaira M. Berdiñas ◽  
Andrea Bonfanti ◽  
...  
Keyword(s):  
Planetary System ◽  
Kuiper Belt ◽  
Dynamical Evolution ◽  
Asteroid Belt ◽  
Physical Parameters ◽  
Planetary Formation ◽  
Low Mass Stars ◽  
The Individual ◽  
The Masses ◽  
M Dwarf

Context. Planets orbiting low-mass stars such as M dwarfs are now considered a cornerstone in the search for planets with the potential to harbour life. GJ 273 is a planetary system orbiting an M dwarf only 3.75 pc away, which is composed of two confirmed planets, GJ 273b and GJ 273c, and two promising candidates, GJ 273d and GJ 273e. Planet GJ 273b resides in the habitable zone. Currently, due to a lack of observed planetary transits, only the minimum masses of the planets are known: Mb sin ib = 2.89 M⊕, Mc sin ic = 1.18 M⊕, Md sin id = 10.80 M⊕, and Me sin ie = 9.30 M⊕. Despite its interesting character, the GJ 273 planetary system has been poorly studied thus far. Aims. We aim to precisely determine the physical parameters of the individual planets, in particular, to break the mass–inclination degeneracy to accurately determine the mass of the planets. Moreover, we present a thorough characterisation of planet GJ 273b in terms of its potential habitability. Methods. First, we explored the planetary formation and hydration phases of GJ 273 during the first 100 Myr. Secondly, we analysed the stability of the system by considering both the two- and four-planet configurations. We then performed a comparative analysis between GJ 273 and the Solar System and we searched for regions in GJ 273 which may harbour minor bodies in stable orbits, that is, the main asteroid belt and Kuiper belt analogues. Results. From our set of dynamical studies, we find that the four-planet configuration of the system allows us to break the mass–inclination degeneracy. From our modelling results, the masses of the planets are unveiled as: 2.89 ≤ Mb ≤ 3.03 M⊕, 1.18 ≤ Mc ≤ 1.24 M⊕, 10.80 ≤ Md ≤ 11.35 M⊕, and 9.30 ≤ Me ≤ 9.70 M⊕. These results point to a system that is likely to be composed of an Earth-mass planet, a super-Earth and two mini-Neptunes. Based on planetary formation models, we determine that GJ 273b is likely an efficient water captor while GJ 273c is probably a dry planet. We find that the system may have several stable regions where minor bodies might reside. Collectively, these results are used to offer a comprehensive discussion about the habitability of GJ 273b.

Silicon and Nickel Enrichment in Planet Host Stars: Observations and Implications for the Core Accretion Theory of Planet Formation

2006 ◽  
Vol 643 (1) ◽  
pp. 484-500 ◽  
Author(s):  
Sarah E. Robinson ◽  
Gregory Laughlin ◽  
Peter Bodenheimer ◽  
Debra Fischer
Keyword(s):  
Planet Formation ◽  
The Core ◽  
Core Accretion ◽  
Host Stars ◽  
Nickel Enrichment

scholarly journals Comets (Existing Populations)

1994 ◽  
Vol 160 ◽  
pp. 77-94
Author(s):  
Ľ. Kresák
Keyword(s):  
Kuiper Belt ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
Survival Times ◽  
Evolutionary Time ◽  
Origin And Evolution ◽  
History Of ◽  
The Individual ◽  
Evolutionary Paths

The definition, population, extent, origin and evolution of the individual subsystems of comets and transitions between them are discussed, together with presentation of the relevant statistical data and their changes with time. The largest outer subsystems are unobservable, but their existence is documented by the necessity of progressive replenishment of the observable populations, with limited survival times. There is persuasive evidence for two different evolutionary paths, one from the Oort cloud and another from the Kuiper belt. While the extent and accuracy of the data available is increasing rapidly, the Jupiter family of comets is the only one for which the evolutionary time scales do not exceed by many orders of magnitude the history of astronomical observations. The individual comet populations differ from one another not only by the distribution of orbits, but also by the size distribution and aging rate of their members. Their dynamical evolution is coupled with disintegration processes, which make it questionable whether the present state can be interpreted as a long-term average.

scholarly journals The Trojan Initiative: A Proposal for a Research Settlement on 2011 HM102 and a Framework for Future Settlement on Asteroids

2021 ◽  
Author(s):  
Briana Chen ◽  
Geetika Chitturi ◽  
Archit Kalra ◽  
Raghav Sriram
Keyword(s):  
Social Life ◽  
Kuiper Belt ◽  
Optical Resolution ◽  
Gluon Plasma ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Oort Cloud ◽  
Water Recovery ◽  
High Energy Radiation ◽  
Oxygen Generation

Humankind has yearned for hundreds of thousands of years to explore and truly understand the dynamics of our enigmatic universe. However, we have often been limited by our hindsight here on Earth, or the limitations of human travel to further destinations. Having the ability to send humans to deep space would arguably set us millions of years ahead in our scientific understanding of various physical processes, including insight on some of the key mysteries that we still face. Perhaps a settlement further away from the Sun, Earth, and limiting optical resolution could provide us with greater ability to collect more meaningful data through our telescopes or other instruments. Moreover, one of the most significant abilities of such a settlement could be slightly easier access to sites of research within our own solar system that could be essential in the forthcoming years, such as Jupiter, Titan, the Kuiper Belt, and some Oort Cloud objects. Here we describe a unique option and set of goals to pursue and achieve just that via a mission to an L5 Trojan asteroid of Neptune, 2011 HM102. In this paper, we propose a number of possible challenges presented by traveling to the base, modeling its layout, maintaining the presence of life, and opportunities for research on the asteroid as well as possible solutions to these challenges. We begin our journey by outlining some motivations for creating a settlement on the asteroid, then outline a few key technological goals that must be achieved before we are capable of efficiently sending a colony of people to the settlement. We describe materials necessary for its construction as well as a novel mechanism for artificial gravity utilizing the Roche limit of the asteroid and multiple applications of quark-gluon plasma. From there we explore more aspects of settlement design, including key considerations for the layout of our settlement, sources of power, and protection from high-energy radiation from sources such as galactic cosmic rays. Then, we embark on a detailed discussion on the measures needed to maintain life on the settlement, such as hydroponic crop growth, a cycle for water recovery and oxygen generation, temperature maintenance, and air purification. Some remarks on the sustainability of life on the settlement follow, as well as some recommendations for entertainment, social life, economics, and governmental systems on the settlement.

Conclusion

2007 ◽  
Author(s):  
Michael B. Miller
Keyword(s):  
Immigration Policy ◽  
Migration Patterns ◽  
The Core ◽  
Mass Migration ◽  
And Migration

This final chapter offers a conclusion to the overall findings of the journal. It summarises the core factors of mass migration: migration patterns and networks; the role of governments and immigration policy; the importance of steamship emigration agents; the business of migration; and the shifting role of ports and port infrastructures. It concludes by suggesting that maritime and migration historians can further their studies by expanding and exploring one another’s territories.

scholarly journals No evidence for interstellar planetesimals trapped in the Solar system

2020 ◽  
Vol 497 (1) ◽  
pp. L46-L49 ◽  
Author(s):  
A Morbidelli ◽  
K Batygin ◽  
R Brasser ◽  
S N Raymond
Keyword(s):  
Solar System ◽  
Oort Cloud ◽  
Giant Planets ◽  
Asteroid Belt ◽  
Interstellar Space ◽  
Fast Decay ◽  
Early Solar System ◽  
The Past ◽  
Solar System Bodies ◽  
Main Asteroid Belt

ABSTRACT In two recent papers published in MNRAS, Namouni and Morais claimed evidence for the interstellar origin of some small Solar system bodies, including: (i) objects in retrograde co-orbital motion with the giant planets and (ii) the highly inclined Centaurs. Here, we discuss the flaws of those papers that invalidate the authors’ conclusions. Numerical simulations backwards in time are not representative of the past evolution of real bodies. Instead, these simulations are only useful as a means to quantify the short dynamical lifetime of the considered bodies and the fast decay of their population. In light of this fast decay, if the observed bodies were the survivors of populations of objects captured from interstellar space in the early Solar system, these populations should have been implausibly large (e.g. about 10 times the current main asteroid belt population for the retrograde co-orbital of Jupiter). More likely, the observed objects are just transient members of a population that is maintained in quasi-steady state by a continuous flux of objects from some parent reservoir in the distant Solar system. We identify in the Halley-type comets and the Oort cloud the most likely sources of retrograde co-orbitals and highly inclined Centaurs.

scholarly journals Deuterium burning in objects forming via the core accretion scenario

2012 ◽  
Vol 547 ◽  
pp. A105 ◽  
Author(s):  
P. Mollière ◽  
C. Mordasini
Keyword(s):  
The Core ◽  
Core Accretion

Planetesimal Capture by an Evolving Giant Gaseous Protoplanet

2012 ◽  
Vol 8 (S293) ◽  
pp. 263-269
Author(s):  
Morris Podolak ◽  
Nader Haghighipour
Keyword(s):  
Mass Distribution ◽  
Total Mass ◽  
Size Composition ◽  
Giant Planets ◽  
The Core ◽  
Last Stage ◽  
Core Accretion ◽  
Gaseous Envelope ◽  
Gas Drag ◽  
Probability Of Capture

AbstractBoth the core-accretion and disk-instability models suggest that at the last stage of the formation of a gas-giant, the core of this object is surrounded by an extended gaseous envelope. At this stage, while the envelope is contracting, planetesimals from the protoplanetary disk may be scattered into the protoplanets atmosphere and deposit some or all of their materials as they interact with the gas. We have carried out extensive simulations of approximately 104 planetesimals interacting with a envelope of a Jupiter-mass protoplanet including effects of gas drag, heating, and the effect of the protoplanets extended mass distribution. Simulations have been carried out for different radii and compositions of planetesimals so that all three processes occur to different degrees. We present the results of our simulations and discuss their implications for the enrichment of ices in giant planets. We also present statistics for the probability of capture (i.e. total mass-deposition) of planetesimals as a function of their size, composition, and closest approach to the center of the protoplanetary body.

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