A UNIFIED THEORY FOR THE EFFECTS OF STELLAR PERTURBATIONS AND GALACTIC TIDES ON OORT CLOUD COMETS

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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3. An Alternate Interpretation of the Oort Cloud of Comets?

International Astronomical Union Colloquium ◽

10.1017/s0252921100069967 ◽

1977 ◽

Vol 39 ◽

pp. 93-97

Author(s):

L. Kresak

Keyword(s):

Relative Size ◽

Oort Cloud ◽

Observational Evidence ◽

The Sun ◽

First Passage ◽

Radiation Mechanism ◽

Original Surface ◽

Significant Difference ◽

First Time ◽

Stellar Perturbations

Some problems of the current interpretation of the Oort Cloud are discussed. If observational selection is taken into account, no significant difference in physical characteristics of old and new comets is apparent, in spite of the required change in the radiation mechanism after the first passage near the Sun. The abundance of new comets puts special requirements on the relative size of the perihelion distances at which they lose their orbital characteristics and original surface properties, respectively. Stellar perturbations do not seem to be effective enough to displace the perihelia of new comets in a single revolution from the zone of insignificant planetary perturbations into the zone of detectability. Therefore, many physically new comets should appear as dynamically old, which is at variance with observational evidence. It is speculated whether the Oort Cloud really represents a reservoir of comets passing near the Sun for the first time or, alternatively, a region where the capability of building up extensive comas is being restored within periods of the order of 106 to 107 years.

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2. Initial Energy and Perihelion Distributions of Oort-Cloud Comets

International Astronomical Union Colloquium ◽

10.1017/s0252921100069955 ◽

1977 ◽

Vol 39 ◽

pp. 87-91 ◽

Cited By ~ 2

Author(s):

P. R. Weissman

Keyword(s):

Monte Carlo ◽

Narrow Range ◽

Monte Carlo Model ◽

Initial Energy ◽

Oort Cloud ◽

Perihelion Distance ◽

Initial States ◽

First Time ◽

Stellar Perturbations

A Monte Carlo model of stellar perturbations of the Oort cloud is used to study the distributions in energy and perihelion of comets entering the planetary region for the first time. The model is run for a variety of initial states and a range of velocity perturbations. In all cases the resulting orbits are uniformly distributed in perihelion distance in the planetary region, q < 20 AU. Most orbits are confined to a fairly narrow range in 1/a and hyperbolic orbits are rare.

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Dynamical Evolution of Trans-Neptunian Objects in High-Eccentricity Orbits

Highlights of Astronomy ◽

10.1017/s1539299600013319 ◽

2002 ◽

Vol 12 ◽

pp. 223-224

Author(s):

V.V. Emel’yanenko

Keyword(s):

Solar System ◽

Inner Core ◽

Dynamical Evolution ◽

Oort Cloud ◽

High Eccentricity ◽

Parabolic Orbits ◽

Stellar Perturbations

AbstractThe evolution of near-parabolic orbits with perihelia in the trans-neptunian region has been studied, considering the action of planetary, Galactic and stellar perturbations for the age of the Solar System. This investigation has led to the conclusion that the observed trans-neptunian objects in high-eccentricity orbits might originate from the inner core of the Oort cloud.

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Injection of Oort Cloud comets: the fundamental role of stellar perturbations

Celestial Mechanics and Dynamical Astronomy ◽

10.1007/s10569-008-9140-y ◽

2008 ◽

Vol 102 (1-3) ◽

pp. 111-132 ◽

Cited By ~ 67

Author(s):

Hans Rickman ◽

Marc Fouchard ◽

Christiane Froeschlé ◽

Giovanni B. Valsecchi

Keyword(s):

Oort Cloud ◽

Stellar Perturbations

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Methods for the Study of the Dynamics of the Oort Cloud Comets I: Modelling the Stellar Perturbations

Topics in Gravitational Dynamics - Lecture Notes in Physics ◽

10.1007/978-3-540-72984-6_9 ◽

2007 ◽

pp. 257-272

Author(s):

Marc Fouchard ◽

Christiane Froeschlé ◽

Hans Rickman ◽

Giovanni B. Valsecchi

Keyword(s):

Oort Cloud ◽

Stellar Perturbations

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Dynamics of comets in the collapsing protosolar nebula

International Astronomical Union Colloquium ◽

10.1017/s0252921100031225 ◽

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.

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From the Oort cloud to Halley-type comets

International Astronomical Union Colloquium ◽

10.1017/s0252921100031638 ◽

1999 ◽

Vol 173 ◽

pp. 327-338 ◽

Cited By ~ 5

Author(s):

J.A. Fernández ◽

T. Gallardo

Keyword(s):

Total Population ◽

Complex Function ◽

Dynamical Evolution ◽

Oort Cloud ◽

Capture Process ◽

Influx Rate ◽

Short Period ◽

Dynamical Properties ◽

Orbital Periods ◽

Probability Of Capture

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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