From the Oort cloud to Halley-type comets

AbstractThe Oort cloud probably is the source of Halley-type (HT) comets and perhaps of some Jupiter-family (JF) comets. The process of capture of Oort cloud comets into HT comets by planetary perturbations and its efficiency are very important problems in comet ary dynamics. A small fraction of comets coming from the Oort cloud − of about 10−2− are found to become HT comets (orbital periods < 200 yr). The steady-state population of HT comets is a complex function of the influx rate of new comets, the probability of capture and their physical lifetimes. From the discovery rate of active HT comets, their total population can be estimated to be of a few hundreds for perihelion distancesq <2 AU. Randomly-oriented LP comets captured into short-period orbits (orbital periods < 20 yr) show dynamical properties that do not match the observed properties of JF comets, in particular the distribution of their orbital inclinations, so Oort cloud comets can be ruled out as a suitable source for most JF comets. The scope of this presentation is to review the capture process of new comets into HT and short-period orbits, including the possibility that some of them may become sungrazers during their dynamical evolution.

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Dynamical evolution of Oort cloud comets to near-Earth space

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307003055 ◽

2006 ◽

Vol 2 (S236) ◽

pp. 43-54 ◽

Cited By ~ 1

Author(s):

Olga A. Mazeeva

Keyword(s):

Dynamical Evolution ◽

Absolute Magnitude ◽

Oort Cloud ◽

Outer Solar System ◽

Earth Space ◽

Near Earth Space ◽

Long Period ◽

Order Of Magnitude ◽

Orbital Periods ◽

Stellar Perturbations

AbstractThe dynamical evolution of 2⋅105 hypothetical Oort cloud comets by the action of planetary, galactic and stellar perturbations during 2⋅109 years is studied numerically. The evolution of comet orbits from the outer (104 AU <a<5⋅104 AU, a is semimajor axes) and the inner Oort cloud (5⋅103 AU <a<104 AU) to near-Earth space is investigated separately. The distribution of the perihelion (q) passage frequency in the planetary region is obtained calculating the numbers of comets in every interval of Δ q per year. The flux of long-period (LP) comets (orbital periods P>200 yr) with perihelion distances q<1.5 AU brighter than visual absolute magnitude H10=7 is ∼ 1.5 comets per year, and ∼18 comets with H10<10.9. The ratio of all LP comets with q<1.5 AU to ‘new’ comets is ∼5. The frequency of passages of LP comets from the inner Oort cloud through region q<1.5 AU is ∼3.5⋅10−13 yr−1, that is roughly one order of magnitude less than frequency of passages of LP comets from the outer cloud (∼5.28⋅10−12 yr−1). We show that the flux of ‘new’ comets with 15<q<31 AU is higher than with q<15 AU, by a factor ∼1.7 for comets from the outer Oort cloud and, by a factor ∼7 for comets from the inner cloud. The perihelia of comets from the outer cloud previously passed through the planetary region are predominated in the Saturn-Uranus region. The majority of inner cloud comets come in the outer solar system (q>15 AU), and a small fraction (∼0.01) of them can reach orbits with q<1.5 AU. The frequency of transfer of comets from the inner cloud (a<104 AU) to the outer Oort cloud (a>104 AU), from where they are injected to the region q<1.5 AU, is ∼6⋅10−14 yr−1.

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Statistical and Evolutionary Aspects of Cometary Orbits

International Astronomical Union Colloquium ◽

10.1017/s0252921100109819 ◽

1989 ◽

Vol 116 (1) ◽

pp. 487-535

Author(s):

J.A. Fernández ◽

W.-H. Ip

Keyword(s):

Molecular Clouds ◽

Oort Cloud ◽

Tidal Force ◽

Time Interval ◽

Mass Relation ◽

Galactic Latitude ◽

Impact Cratering ◽

Influx Rate ◽

Short Period ◽

The Impact

AbstractThe observed frequency of passages of Earth-crossing long-period (LP) comets (P > 200 yr) is about three per year for comets brighter than absolute magnitude H10 ∼ 10.5. About one out of six LP comets is estimated to be new, i.e., making its first passage through the inner planetary region. The sample of observed LP comets shows an excess of retrograde orbits that may be accounted for by the shorter dynamical lifetimes of comets on direct orbits due to planetary perturbations. The original semimajor axes of new comets concentrate in the range 7 × 103 ≳ aorig ≳ 4 × 104 AU, which tells us about the region of the Oort cloud where forces other than planetary perturbations act with the greatest efficiency. Yet the distribution of original semimajor axes cannot tell us anything about the existence of a dense inner core of the Oort cloud. Besides planetary perturbations, passing stars, molecular clouds and the galactic tidal force also influence the dynamical evolution of Oort cloud comets. The observed distribution of the aphelion points of near-parabolic comets shows such a dependence on the galactic latitude. Molecular clouds and stars penetrating very deeply in the Oort cloud are found to give rise to major enhancements in the influx rate of new comets, known as comet showers, at average intervals of a few 107 yr.An important issue to solve concerns how the frequency of comet passages varies with time, in particular as regards to the current level of comet appearances. Should we be passing through a highly intense phase, most aphelia of the incoming Oort comets would concentrate on the sky area where the strong perturber exerted its greatest effect. By contrast, the observed galactic latitude dependence of the aphelia suggests a dominant influence of the vertical galactic tidal force as compared with random strong perturbers. This seems to indicate that the frequency of comet passages is currently at, or near, its quiescent level. Whether intense comet showers are reflected in the impact cratering record is still a debatable issue. A periodicity of ∼ 26-30 Myr in the impact cratering rate is quite uncertain, owing to the small size of the sample of well-dated craters and the noise from background impact craters from asteroids.The family of short-period (SP) comets (orbital periods P < 20 yr) has long been regarded as the dynamical end-state of new comets on low-inclination orbits captured by Jupiter. However, if SP comets came from a spherical population of comets (e.g., incoming new comets), we should expect to find a percentage of them on retrograde orbits, which contradicts the observations. An alternative hypothesis for the origin of most SP comets is that they come from a trans-Neptunian comet belt. Extensive searches aimed at detecting faint slow-moving objects are required to assess the size of the comet population in the outer planetary region. Modeling of the transfer rate of comets from an outer belt to SP orbits gives transient populations between Saturn and Neptune on the order of 106 – 107 bodies. This is roughly comparable to the upper limit set by the most recent searches of outer solar system bodies.The impact crater production rate of comets, at the present time, can be estimated to be on the order of 10% of the value corresponding to asteroidal impacts. These estimates, however, are subject to large uncertainties in the brightness-mass relation of comets and crater scaling law. The Earth could have received about 2 × 1020 g of cometary material over the last 4 billion years — if the injection rate of new comets remained constant in the time interval. Within the context of H2O inventory, the cometary influx should have rather minor effects. On the other hand, because of the paucity of H2O content in the atmospheres of Venus and Mars, cometary impact could strongly modulate their water contents.

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Jupiter’s decisive role in the inner Solar System’s early evolution

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1423252112 ◽

2015 ◽

Vol 112 (14) ◽

pp. 4214-4217 ◽

Cited By ~ 58

Author(s):

Konstantin Batygin ◽

Greg Laughlin

Keyword(s):

Solar System ◽

Dynamical Evolution ◽

Decisive Role ◽

Terrestrial Planets ◽

The Sun ◽

Mean Motion Resonances ◽

The Earth ◽

Short Period ◽

Orbital Periods ◽

Gas Drag

The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System’s terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter’s inward migration entrained s ≳ 10−100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System’s terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution.

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Dynamics and orbital evolution of Oort cloud comets

Symposium - International Astronomical Union ◽

10.1017/s007418090012738x ◽

1996 ◽

Vol 172 ◽

pp. 209-212 ◽

Cited By ~ 1

Author(s):

J.Q. Zheng ◽

M.J. Valtonen ◽

S. Mikkola ◽

H. Rickman

Keyword(s):

Solar System ◽

Orbital Evolution ◽

Oort Cloud ◽

Long Period ◽

Gravitational Perturbations ◽

Short Period ◽

Orbital Periods

Investigators generally conjecture a steady flux of new comets from the Oort cloud through the inner Solar system. Due to gravitational perturbations by major planets these objects may escape, become long period comets (LPCs) if their orbital periods P are larger than 200yr or become short period comets (SPCs) when their period is less than 200yr. SPCs are further divided in two types: the Halley type comets (HT, for P > 20yr) and the Jupiter family comets (JF, for P < 20yr).

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From the Solar system comet cloud to near-Earth space

International Astronomical Union Colloquium ◽

10.1017/s025292110003164x ◽

1999 ◽

Vol 173 ◽

pp. 339-344 ◽

Cited By ~ 1

Author(s):

V.V. Emel'yanenko

Keyword(s):

Steady State ◽

Solar System ◽

Dynamical Evolution ◽

Oort Cloud ◽

High Eccentricity ◽

Earth Space ◽

Near Earth Space ◽

Short Period ◽

Absolute Magnitudes ◽

Continuous Source

AbstractThe dynamical evolution of objects from different zones of the solar system comet cloud to near-Earth space has been investigated. The steady-state number of objects with perihelion distancesq< 1.5 AU and periodsP <20 yr, arising from the near-parabolic flux of comets with absolute magnitudes brighter thanH10= 7 is ∼ 200 − 1000. The corresponding number for Halley-type comets is hundreds of times larger than the number of known Halley-type comets. The flux of objects in the Centaurs zone, captured from the near-parabolic flux is 300 times as large as the flux of new comets. The total number of cometary objects with semi-major axesain the range 50 <a< 500 AU andq∼ 1 AU is ∼ 10 times as large as the number of active comets. The probability of the transfer of objects from the trans-Neptunian orbits with 35 <q< 50 AU anda∼ 600 AU into the Jupiter family is ∼ 0.0001. The calculations show that trans-Neptunian objects on high-eccentricity orbits can be a significant continuous source for both the replenishment of the Oort cloud and the capture to short-period orbits.

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Dynamical Evolution of the Oort Cometary Cloud

Highlights of Astronomy ◽

10.1017/s1539299600005359 ◽

1983 ◽

Vol 6 ◽

pp. 363-370 ◽

Cited By ~ 2

Author(s):

Paul R. Weissman

Keyword(s):

Molecular Clouds ◽

Dynamical Evolution ◽

Oort Cloud ◽

Effective Radius ◽

Giant Molecular Clouds ◽

Monte Carlo Techniques ◽

Short Period ◽

History Of ◽

Hyperbolic Trajectories ◽

Sphere Of Influence

The dynamical evolution of comets in the Oort cloud under the influence of stellar perturbations has been modeled using Monte Carlo techniques. It is shown that the cloud has been depleted over the history of the solar system. Comets are lost from the cloud by direct ejection due to close stellar encounters, diffusion of aphelia to distances beyond the sun’s sphere of influence, or diffusion of perihelia into the planetary region where Jupiter and Saturn perturbations either eject them on hyperbolic trajectories or capture them to short-period orbits. The population of the cloud is estimated to be 1.0 – 1.5 × 1012 comets and the total mass is on the order of 1.9 earth masses. In addition to random passing stars, less frequent encounters with giant molecular clouds may play a significant role in randomizing the orbits of comets in the cloud and reducing the effective radius of the sun’s sphere of influence.

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Dynamical Mechanisms for Transferring Comets In and Out of the Oort Cloud

International Astronomical Union Colloquium ◽

10.1017/s025292110006615x ◽

1993 ◽

Vol 132 ◽

pp. 265-269

Author(s):

M.J. Valtonen ◽

J.Q. Zheng

Keyword(s):

Solar System ◽

Interstellar Medium ◽

Surrounding Medium ◽

Dynamical Evolution ◽

Oort Cloud ◽

Number Density ◽

Upper Limits ◽

Short Period ◽

Comet Orbit

AbstractWe study scenarios where comets are not original members of the Solar System but have been acquired from the surrounding medium through dynamical evolution. This leads to estimates of the present day number density of comets in the interstellar medium which are not in contradiction with observational upper limits. We also consider the dynamical transfer of Oort Cloud comets into short period comets. The process is very sensitive to the inclination of the comet orbit which leads to strong bias in favour of low inclinations in short comet orbits.

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Galactic tide and local stellar perturbations on the Oort cloud: creation of interstellar comets

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935330 ◽

2019 ◽

Vol 629 ◽

pp. A139 ◽

Cited By ~ 9

Author(s):

S. Torres ◽

M. X. Cai ◽

A. G. A. Brown ◽

S. P. Zwart

Keyword(s):

Dynamical Evolution ◽

Cumulative Effect ◽

Oort Cloud ◽

Radial Velocities ◽

Current Status ◽

Interstellar Space ◽

The Sun ◽

Semi Major Axis ◽

Software Environment ◽

External Perturbations

Comets in the Oort cloud evolve under the influence of internal and external perturbations, such as giant planets, stellar passages, and the Galactic gravitational tidal field. We aim to study the dynamical evolution of the comets in the Oort cloud, accounting for the perturbation of the Galactic tidal field and passing stars. We base our study on three main approaches; analytic, observational, and numerical. We first construct an analytical model of stellar encounters. We find that individual perturbations do not modify the dynamics of the comets in the cloud unless very close (<0.5 pc) encounters occur. Using proper motions, parallaxes, and radial velocities from Gaia DR2 and combining them with the radial velocities from other surveys, we then construct an astrometric catalogue of the 14 659 stars that are within 50 pc of the Sun. For all these stars we calculate the time and distance of closest approach to the Sun. We find that the cumulative effect of relatively distant (≤1 pc) passing stars can perturb the comets in the Oort cloud. Finally, we study the dynamical evolution of the comets in the Oort cloud under the influence of multiple stellar encounters from stars that pass within 2.5 pc of the Sun and the Galactic tidal field over ±10 Myr. We use the Astrophysical Multipurpose Software Environment (AMUSE), and the GPU-accelerated direct N-body code ABIE. We considered two models for the Oort cloud, compact (a ≤ 0.25 pc) and extended (a ≤ 0.5 pc). We find that the cumulative effect of stellar encounters is the major perturber of the Oort cloud for a compact configuration while for the extended configuration the Galactic tidal field is the major perturber. In both cases the cumulative effect of distant stellar encounters together with the Galactic tidal field raises the semi-major axis of ~1.1% of the comets at the edge of the Oort cloud up to interstellar regions (a > 0.5 pc) over the 20 Myr period considered. This leads to the creation of transitional interstellar comets (TICs), which might become interstellar objects due to external perturbations. This raises the question of the formation, evolution, and current status of the Oort cloud as well as the existence of a “cloud” of objects in the interstellar space that might overlap with our Oort cloud, when considering that other planetary systems should undergo similar processes leading to the ejection of comets.

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Resonant trans-Neptunian objects as a source of Jupiter-family comets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307003031 ◽

2006 ◽

Vol 2 (S236) ◽

pp. 31-34

Author(s):

E. L. Kiseleva ◽

V. V. Emel'yanenko

Keyword(s):

Solar System ◽

Dynamical Evolution ◽

Early History ◽

Substantial Contribution ◽

Outer Solar System ◽

Symplectic Integrator ◽

Relative Fraction ◽

Outward Transport ◽

Short Period ◽

History Of

AbstractThe dynamical interrelation between resonant trans-Neptunian objects and short-period comets is studied. Initial orbits of resonant objects are based on computations in the model of the outward transport of objects during Neptune's migration in the early history of the outer Solar system. The dynamical evolution of this population is investigated for 4.5 Gyr, using a symplectic integrator. Our calculations show that resonant trans-Neptunian objects give a substantial contribution to the planetary region. We have estimated that the relative fraction of objects captured per year from the 2/3 resonance to Jupiter-family orbits with perihelion distances q<2.5 AU is 0.4×10−10 near the present epoch.

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