scholarly journals Pulsations of Proto-Giant-Planets

1993 ◽  
Vol 139 ◽  
pp. 284-284
Author(s):  
G. Wuchterl
Keyword(s):  
Mass Loss ◽  
Nonlinear Oscillations ◽  
Critical Mass ◽  
Giant Planets ◽  
Quasi Equilibrium ◽  
Planetary Formation ◽  
Instability Strip ◽  
The Earth ◽  
Relative Luminosity ◽  
Two Phases

AbstractNonlinear oscillations of proto-giant-planets have been found in recent numerical calculations relevant to planetary formation. Pulsations are excited in two phases of the protoplanetary evolution, (a) In an ‘instability strip’ at core masses of typically 0.2M⊙ (M⊕ is the earth mass). Perturbations grow into the nonlinear domain and saturate into perodic variations with relative luminosity-amplitudes of 0.2m (b) At the so called critical mass (typically at Mcore ≈ 15M⊕). There the pulsations drive a strong mass loss. A large portion of the envelope is ejected. Then the mass loss fades and the envelope settles into a new quasi-equilibrium. This remnant — a post nucleated instability protoplanet — has a compact envelope and is in core and envelope mass similar to Uranus and Neptune.

scholarly journals Forming terrestrial planets and delivering water

2015 ◽  
Vol 11 (A29B) ◽  
pp. 427-430
Author(s):  
Kevin J. Walsh
Keyword(s):  
Planet Formation ◽  
Semimajor Axis ◽  
Giant Planet ◽  
Terrestrial Planet ◽  
Giant Planets ◽  
Asteroid Belt ◽  
Terrestrial Planets ◽  
The Earth ◽  
Building Models ◽  
Rich Material

AbstractBuilding models capable of successfully matching the Terrestrial Planet's basic orbital and physical properties has proven difficult. Meanwhile, improved estimates of the nature of water-rich material accreted by the Earth, along with the timing of its delivery, have added even more constraints for models to match. While the outer Asteroid Belt seemingly provides a source for water-rich planetesimals, models that delivered enough of them to the still-forming Terrestrial Planets typically failed on other basic constraints - such as the mass of Mars.Recent models of Terrestrial Planet Formation have explored how the gas-driven migration of the Giant Planets can solve long-standing issues with the Earth/Mars size ratio. This model is forced to reproduce the orbital and taxonomic distribution of bodies in the Asteroid Belt from a much wider range of semimajor axis than previously considered. In doing so, it also provides a mechanism to feed planetesimals from between and beyond the Giant Planet formation region to the still-forming Terrestrial Planets.

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 Ram Pressure Stripping of Spiral Galaxies in Clusters

2004 ◽  
Vol 217 ◽  
pp. 376-381
Author(s):  
Elke Schumacher ◽  
Gerhard Hensler
Keyword(s):  
Mass Loss ◽  
Spiral Galaxies ◽  
Disk Galaxies ◽  
Helmholtz Instability ◽  
Restoring Force ◽  
Ram Pressure ◽  
First Results ◽  
Two Phases ◽  
Gas Loss ◽  
Long Timescales

We investigate the process of ram pressure stripping by means of numerical simulations with a 2D hydrodynamical code. We present some first results of a set of simulations with varying galaxy velocities and ICM densities. We find that in typical cluster core environments disk galaxies lose a substantial amount of their gas, whereas in the outskirts of galaxy clusters the mass loss is quite small. Furthermore, the gas loss happens in two phases: In the initial phase gas is pushed out of regions where the ram pressure overcomes the gravitational restoring force; most of the overall gas loss happens in this phase. Afterwards the Kelvin-Helmholtz instability leads to a further mass loss at a small rate, that could be important on long timescales.

scholarly journals Enhanced mass-loss rate evolution of stars with ≳18 M⊙ and missing optically observed type II core-collapse supernovae

2020 ◽  
Vol 494 (4) ◽  
pp. 5230-5238
Author(s):  
Roni Anna Gofman ◽  
Naomi Gluck ◽  
Noam Soker
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Core Collapse ◽  
Type Ii ◽  
Instability Strip ◽  
Stellar Envelope ◽  
Explosion Mechanism ◽  
Hydrogen Mass

ABSTRACT We evolve stellar models with zero-age main-sequence (ZAMS) mass of MZAMS ≳ 18 M⊙ under the assumption that they experience an enhanced mass-loss rate when crossing the instability strip at high luminosities and conclude that most of them end as type Ibc supernovae (SNe Ibc) or dust-obscured SNe II. We explore what level of enhanced mass-loss rate during the instability strip would be necessary to explain the ‘red supergiant problem’. This problem refers to the dearth of observed core-collapse supernovae progenitors with MZAMS ≳ 18 M⊙. Namely, we examine what enhanced mass-loss rate could make it possible for all these stars actually to explode as core-collapse supernovae (CCSNe). We find that the mass-loss rate should increase by a factor of at least about 10. We reach this conclusion by analysing the hydrogen mass in the stellar envelope and the optical depth of the dusty wind at the explosion, and crudely estimate that under our assumptions only about a fifth of these stars explode as unobscured SNe II and SNe IIb. About 10–15 per cent end as obscured SNe II that are infrared-bright but visibly very faint, and the rest, about 65–70 per cent, end as SNe Ibc. However, the statistical uncertainties are still too significant to decide whether many stars with MZAMS ≳ 18 M⊙ do not explode as expected in the neutrino driven explosion mechanism, or whether all of them explode as CCSNe, as expected by the jittering jets explosion mechanism.

scholarly journals The Variability of Critical Mass Loss Rate at Auto-Extinction

2020 ◽  
Author(s):  
Snorri Már Arnórsson ◽  
Rory M. Hadden ◽  
Angus Law
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Critical Mass

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.

Atmospheres of Jupiter and Saturn

1981 ◽  
Vol 303 (1477) ◽  
pp. 225-245 ◽  
Keyword(s):  
Current Knowledge ◽  
Internal Heat ◽  
Giant Planets ◽  
Heat Sources ◽  
The Earth ◽  
International Ultraviolet Explorer ◽  
University College London ◽  
Internal Heat Sources ◽  
Insight Into ◽  
Review Current

In this paper I review current knowledge of the atmospheres of Jupiter and Saturn, making use of the extensive telescopic studies, International Ultraviolet Explorer Satellite observations and the measurements made during the recent Pioneer and Voyager flybys which have been supported by detailed theoretical studies. A detailed discussion is given of the composition of these atmospheres and the abundance ratios which provide insight into their original state and their evolution. The Voyager observations indicate a surprisingly close similarity between the weather systems of the Earth and the giant planets. Although both Jupiter and Saturn have internal heat sources, and are therefore star-like in their interiors, they appear to produce terrestrial-style weather systems. A detailed discussion is given of this work, which forms a major study of the Laboratory for Planetary Atmospheres at University College London.

scholarly journals Dynamical evolution of the Oort cloud

1985 ◽  
Vol 83 ◽  
pp. 87-96
Author(s):  
Paul R. Weissman
Keyword(s):  
Monte Carlo Simulation ◽  
Molecular Clouds ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
Giant Planets ◽  
Giant Molecular Clouds ◽  
The Earth ◽  
The Galaxy ◽  
Periodic Comet ◽  
Monte Carlo Simulation Model

AbstractNew studies of the dynamical evolution of cometary orbits in the Oort cloud are made using a revised version of Weissman’s (1982) Monte Carlo simulation model, which more accurately mimics the perturbation of comets by the giant planets. It is shown that perturbations by Saturn provide a substantial barrier to the diffusion of cometary perihelia into the inner solar system; Jupiter also. Perturbations by Uranus and Neptune are rarely great enough to remove comets from the Oort cloud, but do serve to scatter the comets in the cloud in 1/a. The new model gives a population of 1.8 to 2.1 × 1012 comets for the present-day Oort cloud, and a mass of 7 to 8 earth masses. Perturbation of the Oort cloud by giant molecular clouds in the galaxy is discussed, as is evidence for a massive “inner Oort cloud” internal to the observed one. The possibility of an unseen solar companion orbiting in the Oort cloud and causing periodic comet showers is shown to be dynamically plausible but unlikely based on the observed cratering rate on the earth and moon.

scholarly journals Cepheid Evolution with Pulsationally-Driven Mass Loss

1989 ◽  
Vol 111 ◽  
pp. 252-252 ◽  
Author(s):  
Wendee M. Brunish ◽  
Lee Anne Willson
Keyword(s):  
Mass Loss ◽  
Instability Strip

AbstractWe have studied the effects of a pulsationally-driven wind on Cepheid evolution. Mass loss due to the wind, which occurs only when the star is crossing the Cepheid instability strip, is a function of luminosity and radius. We have investigated the evolution of 4, 5, 6, 7 and 8 M⊙ stars using the updated 12C(α,γ) 16O rates.

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