Stellar Encounters with the Oort Cloud Based on [ITAL]Hipparcos[/ITAL] Data

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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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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Long-term evolution of Oort Cloud comets: capture of comets

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.2002.05460.x ◽

2002 ◽

Vol 333 (4) ◽

pp. 835-846 ◽

Cited By ~ 6

Author(s):

P. Nurmi ◽

M. J. Valtonen ◽

J. Q. Zheng ◽

H. Rickman

Keyword(s):

Long Term Evolution ◽

Oort Cloud ◽

Term Evolution

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Comparison of original orbits of Oort Cloud new comets given in various catalogues

10.1002/essoar.10503960.1 ◽

2020 ◽

Author(s):

Takashi Ito

Keyword(s):

Oort Cloud

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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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