scholarly journals Dynamics of Comets: Recent Developments and New Challenges

1994 ◽  
Vol 160 ◽  
pp. 223-240
Author(s):  
Julio A. Fernández
Keyword(s):  
Solar System ◽  
Inner Core ◽  
Galactic Disk ◽  
Kuiper Belt ◽  
Oort Cloud ◽  
Tidal Force ◽  
Giant Molecular Clouds ◽  
Recent Developments ◽  
Large Telescopes ◽  
Classical Picture

There is a broad consensus that long-period comets come from a huge reservoir surrounding the solar system, as proposed originally by Oort. Yet, the classical picture of the Oort cloud has substantially changed during the last decade. In addition to passing stars, the tidal force of the galactic disk and giant molecular clouds have also been identified as major perturbers of the Oort cloud. In particular, the latter may be responsible for limiting the size of the stable Oort cloud to no more than ≈ 104AU, i.e. about one tenth of the classical Oort's radius.Most comets are injected into the planetary region by the quasi-steady action of the tidal force of the galactic disk. The concentration of aphelion points of dynamically young comets toward mid-galactic latitudes is a consequence of its dominant influence. The frequency of comet passages into the inner planetary region could experience significant fluctuations with time as the Oort cloud meets random strong perturbers. The observed ordered pattern of most comet aphelia, associated with the galactic structure, argues against a recent strong perturbation of the Oort cloud.The origin of the Jupiter family has become another point of intense debate. Jupiter family comets may come from a transneptunian comet belt -the Kuiper belt- from where they can reach the planetary region through chaotic motion. The Kuiper belt has become accessible to large telescopes, as shown by the recent discoveries of 1992QB1 and 1993FW, possibly belt members. The major challenge will be to explore the region usually inaccessible to external perturbers that goes from ~30 AU to a few thousand AU. A significant mass may have been locked there from the beginnings of the solar system, giving rise to an inner core that feeds the outer or classical Oort cloud. Our aim will be to briefly discuss some of the topics summarized here.

A Brief Summary of Kuiper Belt Research

1998 ◽  
Vol 11 (1) ◽  
pp. 223-228
Author(s):  
R. Malhotra
Keyword(s):  
Solar System ◽  
Solar Nebula ◽  
Kuiper Belt ◽  
Oort Cloud ◽  
Theoretical Argument ◽  
Numerical Work ◽  
Small Bodies ◽  
Considerable Difficulty ◽  
Long Period ◽  
Short Period

Ideas about the contents of the Solar System beyond Neptune and Pluto can be traced back to at least Edgeworth (1943, 1949) and Kuiper (1951), who speculated on the existence of pre-planetary small bodies in the outer Solar System beyond the orbit of Neptune - remnants of the accretion process in the primordial Solar Nebula. The basis for the speculation was primarily the argument that the Solar Nebula was unlikely to have been abruptly truncated at the orbit of Neptune, and that in the trans-Neptunian accretion timescales were too long for bodies larger than about ˜ 1000 km in radius to have formed in the 4.5 billion year age of the Solar System. Another important theoretical argument relevant to this region of the Solar System is related to the origin of short period comets. Fernández (1980) suggested that the short period comets may have an origin in a disk of small bodies beyond Neptune, rather than being “captured” from the population of long period comets originating in the Oort Cloud, the latter scenario having considerable difficulty reconciling the observed flux of short period comets with the exceedingly low efficiency of transfer of long period comet orbits to short period ones by means of the gravitational perturbations of the giant planets. The new scenario received further strength in the numerical work of Duncan et al. (1988) and Quinn et al. (1990) which showed that the relatively small orbital inclinations of the Jupiter-family short period comets were not consistent with a source in the isotropic Oort Cloud of comets but could be reproduced with a source in a low-inclination reservoir beyond Neptune’s orbit. Duncan et al. named this hypothetical source the Kuiper Belt, and the name has come into common use in the last decade (although other names are also in use, e.g. Edgeworth-Kuiper Belt, and trans-Neptunian objects). A recent theoretical milestone was the work by Holman and Wisdom (1993) and Levison and Duncan (1993) on the long term stability of test particle orbits in the trans-Neptunian Solar System. This work showed that low-eccentricity, low-inclination orbits with semimajor axes in excess of about 43 AU are stable on billion year timescales, but that in the region between 35 AU and 43 AU orbital stability times range from 107 yr to more than 109 yr [see, for example, figure 1 in Holman (1995)]. Orbital instability in this intermediate region typically leads to a close encounter with Neptune which causes dramatic orbital changes, with the potential for subsequent transfer to the inner Solar System. Thus, this region could in principle serve as the reservoir of short period comets at the present epoch. However, the idea of a kinematically cold — i.e. low-eccentricity, low-inclination — population in this region is at odds with recent observations, and the question of the origin of short period comets remains unsettled at the present time.

scholarly journals The fate of planetesimal discs in young open clusters: implications for 1I/’Oumuamua, the Kuiper belt, the Oort cloud, and more

2019 ◽  
Vol 490 (1) ◽  
pp. 21-36 ◽  
Author(s):  
T O Hands ◽  
W Dehnen ◽  
A Gration ◽  
J Stadel ◽  
B Moore
Keyword(s):  
Solar System ◽  
Graphics Processing Units ◽  
Open Cluster ◽  
Kuiper Belt ◽  
Large Population ◽  
Oort Cloud ◽  
Open Clusters ◽  
Cluster Evolution ◽  
Exoplanetary Systems ◽  
Test Particles

ABSTRACT We perform N-body simulations of the early phases of open cluster evolution including a large population of planetesimals, initially arranged in Kuiper-belt like discs around each star. Using a new, fourth-order, and time-reversible N-body code on Graphics Processing Units (GPUs), we evolve the whole system under the stellar gravity, i.e. treating planetesimals as test particles, and consider two types of initial cluster models, similar to IC348 and the Hyades, respectively. In both cases, planetesimals can be dynamically excited, transferred between stars, or liberated to become free-floating (such as A/2017 U1 or ’Oumuamua) during the early cluster evolution. We find that planetesimals captured from another star are not necessarily dynamically distinct from those native to a star. After an encounter, both native and captured planetesimals can exhibit aligned periastrons, qualitatively similar to that seen in the Solar system and commonly thought to be the signature of Planet 9. We discuss the implications of our results for both our Solar system and exoplanetary systems.

scholarly journals The Galactic Disk Tidal Force: Simulating the Observed Oort Cloud Comets

1997 ◽  
Vol 165 ◽  
pp. 149-154
Author(s):  
P. A. Dybczyński ◽  
H. Prȩtka
Keyword(s):  
Detailed Analysis ◽  
Galactic Disk ◽  
Equations Of Motion ◽  
Threshold Value ◽  
Oort Cloud ◽  
Tidal Force ◽  
Statistical Characteristics ◽  
Perihelion Distance ◽  
Osculating Elements ◽  
Averaged Hamiltonian

In previous papers (Prȩtka and Dybczyński, 1994; Dybczyński and Prȩtka, 1996) we presented detailed analysis of selected examples of the long-term evolution of the orbit of Oort cloud comets under the influence of the galactic disk tidal force, as well as some statistical characteristics of the simulated observable comet population. This paper presents further improvements in our Monte Carlo simulation programme which allow us to represent in a better way the real processes of production of observable comets due to galactic perturbations.In our second paper (Dybczyński and Prȩtka, 1996), following some other authors (see for example Matese and Whitman, 1989), we treated a comet as observable when its osculating perihelion distance decreased below some adopted observability limit (5 AU in our case). Limiting the investigation to the evolution of osculating elements allowed us to use very fast and efficient averaged Hamiltonian equations of motion in our simulation. However, further detailed analysis of the problem showed that the adopted observability definition was insufficient: what makes a comet observable is not its osculating perihelion distance but its true distance from the Sun, smaller than some adopted threshold value. It may happen that when the osculating perihelion distance is at its smallest, the comet is around its aphelion distance.

scholarly journals Variability of The Oort Cloud Comet Flux: Can It be Manifest in The Cratering Record?

1998 ◽  
Vol 11 (1) ◽  
pp. 252-256
Author(s):  
J.J. Matese ◽  
P.G. Whitman ◽  
K.A. Innanen ◽  
M.J. Valtonen
Keyword(s):  
Time Series ◽  
Solar System ◽  
Galactic Disk ◽  
Accurate Determination ◽  
Oscillation Period ◽  
Oort Cloud ◽  
Solar Oscillation ◽  
Oscillation Phase ◽  
Stellar Velocity ◽  
Long Time

Abstract We consider the subject of time dependence of the Oort cloud comet flux. Over long time scales the flux is likely to be dominated by the adiabatic galactic tide. This tide is substantially modulated as the Solar System moves in its galactic orbit. If Shoemaker was correct in his estimate that virtually all terrestrial craters of diameter > 100 km are produced by long period comets, then the phase and plane crossing period of the Solar System about the galactic disk should be consistent. with the ages of accurately dated large craters. A time series analysis of these ages in which the Solar oscillation phase is fixed to be consistent with observations indicates a maximal correlation for a period of 36 ± 2 Myr. This period is well within observational limits. If improvements in stellar velocity dispersion studies continue, it is possible that a sufficiently accurate determination of the Solar oscillation period can be found to unambiguously answer the following questions. Is the Solar oscillation cycle correlated with the time series of ages for large craters? If so, can we reject the hypothesis that the correlation is an artifact that could likely be reproduced by a random distribution of ages? We present evidence which suggests that if it is found that the data requires a plane crossing period in the range 36 ± 2 Myr, the answer to both of these questions will be affirmative.

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

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.

Persistent hazardous environments around stars older than the Sun

2006 ◽  
Vol 5 (3) ◽  
pp. 187-190 ◽  
Author(s):  
J.S. Greaves
Keyword(s):  
Solar System ◽  
Kuiper Belt ◽  
The Sun ◽  
Hazardous Environments ◽  
Debris Particles ◽  
Recovery Times ◽  
Nearby Stars ◽  
History Of ◽  
Large Telescopes ◽  
Long Timescales

Collisions amongst comets create belts of orbiting debris and, by using submillimetre wavelength observations, these collision zones can be imaged around nearby stars. An image of the closest Solar analogue, τ Ceti, shows that it possesses at least 20 times the content of the outer Solar System in cool debris particles. The inferred population of parent colliders is around 1 M[oplus ], also much larger than in the Sun's Kuiper Belt of comets. This system represents a different evolutionary outcome for a Sun-like star, with no Jupiter-like planet but many cometary bodies, and thus a potentially heavy and prolonged history of impacts on any inner terrestrial planets. Since τ Ceti is 10 Gyr old, life would have had to deal with massive bombardment over very long timescales. Furthermore, impactors in the 10 km-upwards class could arrive at intervals of 1 Myr or less, longer than recovery times on Earth, and so similar biology is unlikely. It is presently unknown whether nearby stars typically have comet belts similar to that of the Sun or of τ Ceti; extrapolations of existing data suggest many stars could be at least 2–5 times above the Solar debris level. Future large telescopes will be able to probe down to Solar System levels of cometary debris.

scholarly journals Nature and History of the Organic Compounds in Comets: an Astrophysical View

1989 ◽  
Vol 116 (1) ◽  
pp. 377-428
Author(s):  
A.H. Delsemme
Keyword(s):  
Solar System ◽  
Kuiper Belt ◽  
Oort Cloud ◽  
Carbonaceous Chondrites ◽  
Interstellar Molecules ◽  
Subsequent Formation ◽  
History Of ◽  
Probable Origin ◽  
Exogenous Origin ◽  
Two Populations

AbstractThe chemical similarities between comets, carbonaceous chondrites, and interstellar molecules and grains are reviewed first. The evolution of frosty interstellar grains is then followed during the collapse of a molecular cloud fragment and the subsequent formation of the Solar System. The paradigm clarifies the probable origin of the two populations of comets of different symmetry (the Oort Cloud and the Kuiper Belt) and implies an exogenous origin for all carbon and water on Earth. This origin is explained by the orbital diffusion of planetesimals that is required by the growth of protoplanets.

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 Comets

1998 ◽  
Vol 11 (2) ◽  
pp. 1155-1156
Author(s):  
H.U. Keller
Keyword(s):  
Solar System ◽  
Physical Properties ◽  
Data Reduction ◽  
Kuiper Belt ◽  
Preliminary Results ◽  
Open Time ◽  
Transneptunian Objects ◽  
Selection For

Comets, the most pristine members of our solar system, are faint at large heliocentric distances (rh > 3 au) and therefore difficult to observe. Data reduction of these faint objects (periodic comets) is time consuming and hence most often just preliminary results can be discussed. Only the orbits of short periodic comets can be predicted and most of those that have been accessible for ISO have been covered within the guaranteed time programme. About 10 proposals were accepted by the selection for open time proposals. A target of opportunity team was formed. The outstanding comet Hale-Bopp (C/1995 01), one of the brightest and therefore most active comets of this century, was suggested and accepted as TOO. The important results from the ISO cometary programme are derived from its observations. In addition to the observations of "classic" comets the newly detected (Jewitt and Luu, 1993) transneptunian objects, probably objects from the Kuiper belt, are observed in an attempt to determine their physical properties.

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