Dynamics of comets in the collapsing protosolar nebula

1999 ◽  
Vol 173 ◽  
pp. 45-50
Author(s):  
L. Neslušan
Keyword(s):  
Solar System ◽  
Velocity Distribution ◽  
Oort Cloud ◽  
Interstellar Clouds ◽  
Protosolar Nebula ◽  
Moving Bodies

AbstractComets are created in the cool, dense regions of interstellar clouds. These macroscopic bodies take place in the collapse of protostar cloud as mechanically moving bodies in contrast to the gas and miscroscopic dust holding the laws of hydrodynamics. In the presented contribution, there is given an evidence concerning the Solar system comets: if the velocity distribution of comets before the collapse was similar to that in the Oort cloud at the present, then the comets remained at large cloud-centric distances. Hence, the comets in the solar Oort cloud represent a relict of the nebular stage of the Solar system.

scholarly journals Light propagation in the Solar System for astrometry on sub-micro-arcsecond level

2017 ◽  
Vol 12 (S330) ◽  
pp. 106-107
Author(s):  
Sven Zschocke
Keyword(s):  
Solar System ◽  
Rotational Motion ◽  
Arbitrary Shape ◽  
Light Propagation ◽  
List Type ◽  
Type Number ◽  
Recent Advancement ◽  
Moving Bodies

AbstractWe report on recent advancement in the theory of light propagation in the Solar System aiming at sub-micro-arcsecond level of accuracy: (1)A solution for the light ray in 1.5PN approximation has been obtained in the field of N arbitrarily moving bodies of arbitrary shape, inner structure, oscillations, and rotational motion.(2)A solution for the light ray in 2PN approximation has been obtained in the field of one arbitrarily moving pointlike body.

scholarly journals Supportive Evidence for a Brown Dwarf Solar Companion

2004 ◽  
Vol 202 ◽  
pp. 214-216
Author(s):  
John J. Matese
Keyword(s):  
Solar System ◽  
Oort Cloud ◽  
Evidence Based ◽  
Supportive Evidence ◽  
Orbital Elements ◽  
Brown Dwarf ◽  
Wide Binary ◽  
Gas Giant ◽  
Binary Object

We have previously given evidence based on Oort cloud comet orbital elements which suggested that there may be a Jovian-mass brown dwarf in our solar system. An extended cometary database is now available. The analyses have been repeated and we find that the set of statistically significant correlated anomalies is enhanced. We also respond to unsupported objections that have been raised to this conjecture. If real, the wide-binary object would constitute a natural dynamical intermediary between gas giant planetary objects and isolated objects.

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 Isotopic Ratios in Comets

1991 ◽  
Vol 116 (2) ◽  
pp. 879-895 ◽  
Author(s):  
V. Vanysek
Keyword(s):  
Isotopic Ratio ◽  
Chemical Fractionation ◽  
Interstellar Clouds ◽  
Outer Planets ◽  
Carbon Isotopic Ratio ◽  
Carbon Isotopic ◽  
Nuclear Species ◽  
Carbon Reservoir ◽  
Protosolar Nebula ◽  
The Individual

Abstract.The isotopic abundances depend on the universal evolution of elements and on the individual history of particular objects. Since it is believed that unprocessed material of the solar nebula is preserved in comets, the data concerning the abundance of stable isotopes in these primitive bodies are of some importance in the cosmological context. The present status of this problem is reviewed. The reliability of results for nuclear species with cosmological and cosmogonical implications, such as D/H, C 12/13, N 14/15, O 16/18, and Mg 24/25/26, is discussed. Significant variation is found for the isotopic abundance of carbon, depending upon which carbon reservoir is sampled. Deuterium is probably enhanced relative to the interstellar ratio. For other isotopes, the ratios are close to those of the terrestrial data. The tendency of the D/H ratio to be at higher values indicates a low temperature in the environment of the comet’s formation, and, together with similar effects in the outer planets, suggests that there were two different primordial reservoirs of deuterium in the solar system. The 12C/13C ratio inferred from in situ mass spectrometry of the dust, as well as from the ground-based optical spectra of the Swan band, tends to be approximately equal to the average terrestrial ratio (89) or larger. Recent results obtained from the CN band provide a significantly lower value (about 65), which corresponds to the carbon isotopic ratio in the diffuse interstellar clouds. The enhancement of deuterium and the possible differences of the carbon isotopic ratio in different species and refractory material are indicative of chemical fractionation processes in the protosolar nebula.

scholarly journals A Speculation into the Origin of Neutral Globules in Planetary Nebulae: Could the Helix’s Comets Really be Comets?

1995 ◽  
Vol 12 (2) ◽  
pp. 170-173
Author(s):  
Grant Gussie
Keyword(s):  
Solar System ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Oort Cloud ◽  
Asymptotic Giant Branch ◽  
Neutral Gas ◽  
Red Giant ◽  
The Masses

AbstractA novel explanation for the origin of the cometary globules within NGC 7293 (the ‘Helix’ planetary nebula) is examined, namely that these globules originate as massive cometary bodies at large astrocentric radii. The masses of such hypothetical cometary bodies would have to be several orders of magnitude larger than those of any such bodies observed in our solar system in order to supply the observed mass of neutral gas. It is, however, shown that comets at ‘outer Oort cloud’ distances are likely to survive past the red giant and asymptotic giant branch evolutionary phases of the central star, allowing them to survive until the formation of the planetary nebula. Some observational tests of this hypothesis are proposed.

scholarly journals Planetary Trojans – the main source of short period comets?

2010 ◽  
Vol 9 (4) ◽  
pp. 227-234 ◽  
Author(s):  
J. Horner ◽  
P. S. Lykawka
Keyword(s):  
Solar System ◽  
Short Review ◽  
Oort Cloud ◽  
Asteroid Belt ◽  
Exoplanetary Systems ◽  
Short Period ◽  
Proximate Source ◽  
Different Origins ◽  
Near Earth Asteroids ◽  
The Impact

AbstractOne of the key considerations when assessing the potential habitability of telluric worlds will be that of the impact regime experienced by the planet. In this work, we present a short review of our understanding of the impact regime experienced by the terrestrial planets within our own Solar system, describing the three populations of potentially hazardous objects which move on orbits that take them through the inner Solar system. Of these populations, the origins of two (the Near-Earth Asteroids and the Long-Period Comets) are well understood, with members originating in the Asteroid belt and Oort cloud, respectively. By contrast, the source of the third population, the Short-Period Comets, is still under debate. The proximate source of these objects is the Centaurs, a population of dynamically unstable objects that pass perihelion (closest approach to the Sun) between the orbits of Jupiter and Neptune. However, a variety of different origins have been suggested for the Centaur population. Here, we present evidence that at least a significant fraction of the Centaur population can be sourced from the planetary Trojan clouds, stable reservoirs of objects moving in 1:1 mean-motion resonance with the giant planets (primarily Jupiter and Neptune). Focussing on simulations of the Neptunian Trojan population, we show that an ongoing flux of objects should be leaving that region to move on orbits within the Centaur population. With conservative estimates of the flux from the Neptunian Trojan clouds, we show that their contribution to that population could be of order ~3%, while more realistic estimates suggest that the Neptune Trojans could even be the main source of fresh Centaurs. We suggest that further observational work is needed to constrain the contribution made by the Neptune Trojans to the ongoing flux of material to the inner Solar system, and believe that future studies of the habitability of exoplanetary systems should take care not to neglect the contribution of resonant objects (such as planetary Trojans) to the impact flux that could be experienced by potentially habitable worlds.

Noble Gases

2018 ◽  
Author(s):  
Mario Trieloff
Keyword(s):  
Solar System ◽  
Noble Gases ◽  
Noble Gas ◽  
Asteroid Belt ◽  
Element Abundance ◽  
Terrestrial Planets ◽  
Abundance Pattern ◽  
Terrestrial Atmosphere ◽  
The Earth ◽  
Protosolar Nebula

Although the second most abundant element in the cosmos is helium, noble gases are also called rare gases. The reason is that they are not abundant on terrestrial planets like the Earth, which is characterized by orders of magnitude depletion of—particularly light—noble gases when compared to the cosmic element abundance pattern. Indeed, geochemical depletion and enrichment processes mean that noble gases are highly versatile tracers of planetary formation and evolution. When our solar system formed—or even before—small grains and first condensates incorporated small amounts of noble gases from the surrounding gas of solar composition, resulting in depletion of light He and Ne relative to heavy Ar, Kr, and Xe, leading to the “planetary type” abundance pattern. Further noble gas depletion occurred during flash heating of mm- to cm-sized objects (chondrules and calcium, aluminum-rich inclusions), and subsequently during heating—and occasionally differentiation—on small planetesimals, which were precursors of planets. Some of these objects are present today in the asteroid belt and are the source of many meteorites. Many primitive meteorites contain very small (micron to sub-micron size) rare grains that are older than our Solar System and condensed billions of years ago in in the atmospheres of different stars, for example, Red Giant stars. These grains are characterized by nucleosynthetic anomalies, in particular the noble gases, such as so-called s-process xenon. While planetesimals acquired a depleted noble gas component strongly fractionated in favor of heavy noble gases, the Sun and also gas giants like Jupiter attracted a much larger amount of gas from the protosolar nebula by gravitational capture. This resulted in a cosmic or “solar type” abundance pattern, containing the full complement of light noble gases. In contrast, terrestrial planets accreted from planetesimals with only minor contributions from the gaseous component of the protosolar nebula, which accounts for their high degree of depletion and essentially “planetary” elemental abundance pattern. The strong depletion in noble gases facilitates their application as noble gas geo- and cosmochronometers; chronological applications are based on being able to determine noble gas isotopes formed by radioactive decay processes, for example, 40Ar by 40K decay, 129Xe by 129I decay, or fission Xe from 238U or 244Pu decay. Particularly ingrowth of radiogenic xenon is only possible due to the depletion of primordial nuclides, which allows insight into the chronology of fractionation of lithophile parent nuclides and atmophile noble gas daughters. Applied to large-scale planetary reservoirs, this helps to elucidate the timing of mantle degassing and evolution of planetary atmospheres. Applied to individual rocks and minerals, it allows radioisotope chronology using short-lived (e.g., 129I–129Xe) or long-lived (e.g., 40K–40Ar) systems. The dominance of 40Ar in the terrestrial atmosphere allowed von Weizsäcker to conclude that most of the terrestrial atmosphere originated by degassing of the solid Earth, which is an ongoing process today at mid-ocean ridges, as indicated by outgassing of primordial helium from newly forming ocean crust. Mantle degassing was much more massive in the past, with most of the terrestrial atmosphere probably formed during the first few 100 million years of Earth’s history, in response to major evolutionary processes of accretion, terrestrial core formation, and the terminal accretion stage of a giant impact that formed our Moon. During accretion, solar noble gases were added to the mantle, presumably by solar wind irradiation of the small planetesimals and dust accreting to form the Earth. While the Moon-forming impact likely dissipated a major fraction of the primordial atmosphere, today’s atmosphere originated by addition of a late veneer of asteroidal and possibly cometary material combined with a decreasing rate of mantle degassing over time. As other atmophile elements behave similarly to noble gases, they also trace the origin of major volatiles on Earth, for example, water, nitrogen, and carbon.

Accretion Processes

2018 ◽  
Author(s):  
Alessandro Morbidelli
Keyword(s):  
Solar System ◽  
Total Mass ◽  
Extrasolar Planets ◽  
Initial Conditions ◽  
Oort Cloud ◽  
Planetary Science ◽  
Solid Particles ◽  
Giant Planets ◽  
Irregular Satellites ◽  
Accretion Process

In planetary science, accretion is the process in which solids agglomerate to form larger and larger objects, and eventually planets are produced. The initial conditions are a disc of gas and microscopic solid particles, with a total mass of about 1% of the gas mass. These discs are routinely detected around young stars and are now imaged with the new generation of instruments. Accretion has to be effective and fast. Effective, because the original total mass in solids in the solar protoplanetary disk was probably of the order of ~300 Earth masses, and the mass incorporated into the planets is ~100 Earth masses. Fast, because the cores of the giant planets had to grow to tens of Earth masses to capture massive doses of hydrogen and helium from the disc before the dispersal of the latter, in a few millions of years. The surveys for extrasolar planets have shown that most stars have planets around them. Accretion is therefore not an oddity of the solar system. However, the final planetary systems are very different from each other, and typically very different from the solar system. Observations have shown that more than 50% of the stars have planets that don’t have analogues in the solar system. Therefore the solar system is not the typical specimen. Models of planet accretion have to explain not only how planets form, but also why the outcomes of the accretion history can be so diverse. There is probably not one accretion process but several, depending on the scale at which accretion operates. A first process is the sticking of microscopic dust into larger grains and pebbles. A second process is the formation of an intermediate class of objects called planetesimals. There are still planetesimals left in the solar system. They are the asteroids orbiting between the orbits of Mars and Jupiter, the trans-Neptunian objects in the distant system, and other objects trapped along the orbits of the planets (Trojans) or around the giant planets themselves (irregular satellites). The Oort cloud, source of the long period comets, is also made of planetesimals ejected from the region of formation of the giant planets. A third accretion process has to lead from planetesimals to planets. Actually, several processes can be involved in this step, from collisional coagulation among planetesimals to the accretion of small particles under the effect of gas drag, to giant impacts between protoplanets. Adopting a historical perspective of all these processes provides details of the classic processes investigated in the past decades to those unveiled in the last years. The quest for planet formation is ongoing. Open issues remain, and exciting future developments are expected.

Noble Gases

2017 ◽  
Author(s):  
Mario Trieloff
Keyword(s):  
Solar System ◽  
Noble Gases ◽  
Noble Gas ◽  
Asteroid Belt ◽  
Element Abundance ◽  
Terrestrial Planets ◽  
The Sun ◽  
Abundance Pattern ◽  
Terrestrial Atmosphere ◽  
Protosolar Nebula

This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Although the second most abundant element in the cosmos is helium, noble gases are also called rare gases. The reason is that they are not abundant on terrestrial planets like our Earth, which is characterized by orders of magnitude depletion of—particularly light—noble gases when compared to the cosmic element abundance pattern. Indeed, such geochemical depletion and enrichment processes make noble gases so versatile concerning planetary formation and evolution: When our solar system formed, the first small grains started to adsorb small amounts of noble gases from the protosolar nebula, resulting in depletion of light He and Ne when compared to heavy noble gases Ar, Kr, and Xe: the so-called planetary type abundance pattern. Subsequent flash heating of the first small mm to cm-sized objects (chondrules and calcium, aluminum rich inclusions) resulted in further depletion, as well as heating—and occasionally differentiation—on small planetesimals, which were precursors of larger planets and which we still find in the asteroid belt today from where we get rocky fragments in form of meteorites. In most primitive meteorites, we even can find tiny rare grains that are older than our solar system and condensed billions of years ago in circumstellar atmospheres of, for example, red giant stars. These grains are characterized by nucleosynthetic anomalies and particularly identified by noble gases, for example, so-called s-process xenon.While planetesimals acquired a depleted noble gas component strongly fractionated in favor of heavy noble gases, the sun and also gas giants like Jupiter attracted a much larger amount of gas from the protosolar nebula by gravitational capture. This resulted in a cosmic or “solar type” abundance pattern, containing the full complement of light noble gases. Contrary to Jupiter or the sun, terrestrial planets accreted from planetesimals with only minor contributions from the protosolar nebula, which explains their high degree of depletion and basically “planetary” elemental abundance pattern. Indeed this depletion enables another tool to be applied in noble gas geo- and cosmochemistry: ingrowth of radiogenic nuclides. Due to heavy depletion of primordial nuclides like 36Ar and 130Xe, radiogenic ingrowth of 40Ar by 40K decay, 129Xe by 129I decay, or fission Xe from 238U or 244Pu decay are precisely measurable, and allow insight in the chronology of fractionation of lithophile parent nuclides and atmophile noble gas daughters, mainly caused by mantle degassing and formation of the atmosphere.Already the dominance of 40Ar in the terrestrial atmosphere allowed C. F v. Weizsäcker to conclude that most of the terrestrial atmosphere originated by degassing of the solid Earth, which is an ongoing process today at mid ocean ridges, where primordial helium leaves the lithosphere for the first time. Mantle degassing was much more massive in the past; in fact, most of the terrestrial atmosphere formed during the first 100 million years of Earth´s history, and was completed at about the same time when the terrestrial core formed and accretion was terminated by a giant impact that also formed our moon. However, before that time, somehow also tiny amounts of solar noble gases managed to find their way into the mantle, presumably by solar wind irradiation of small planetesimals or dust accreting to Earth. While the moon-forming impact likely dissipated the primordial atmosphere, today´s atmosphere originated by mantle degassing and a late veneer with asteroidal and possibly cometary contributions. As other atmophile elements behave similar to noble gases, they also trace the origin of major volatiles on Earth, for example, water, nitrogen, sulfur, and carbon.

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