The Evolution of Long-Period Comets

Wiegert, Paul; Tremaine, Scott

doi:10.1006/icar.1998.6040

Cited by 174 publications

(237 citation statements)

References 77 publications

(172 reference statements)

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“…Our results on the number of injected, quiescent comets are in general agreement with the location of synthetic Oort spikes found by others using similar experiments (e.g., Wiegert & Tremaine 1999;Emel'yanenko et al 2007). Our maximum of the injection efficiency occurs around 33 000 AU.…”

Section: The Injected Cometssupporting

confidence: 92%

The last revolution of new comets: the role of stars and their detectability

Fouchard

Rickman

Froeschlé

et al. 2011

A&A

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Context. This work is a follow-up of a previous study, where we simulated the dynamical evolution of the Oort Cloud over 5 Gyr with special attention to the injection of comets into observable orbits. Aims. We wish to clarify how comet injection operates with two types of perturbers: Galactic tides and passing stars. We illustrate why attempts to identify the stars that might have played an important role in injecting the observed new Oort Cloud comets are as yet unlikely to succeed, and investigate how large an improvement can be expected from the Gaia mission. Methods. We simulate a 5 Gyr time span, concentrating on the injections found during the last 3 Gyr by extracting detailed information about the last revolution of the injected comets. We analyse the contributions of both the Galactic tides and the stars separately, and assess their importance as a function of the semi-major axis of the comets. We also compute the distances and motions of the perturbing stars at the time the comets reach their perihelia and thus estimate their observability. Results. By studying more than 20 000 injected comets, we determine how the likelihood of tidal and stellar injections varies with the semi-major axis. We establish the range of semi-major axis for which a real-time synergy between stellar and tidal perturbations is important. We find how many perturbing stars could be identified using Hipparcos and Gaia data, and how the dynamics of injections would change, if only the observable stars were acting. Conclusions. The number of injected comets peaks at a semi-major axis (a) of about 33 000 AU but the comets spread over a wide range around this value. The tides are unable to inject any comets at a < 23 000 AU but would be able to inject almost all of them at a > 50 000 AU. The real-time synergy is found to extend between a ∼ 15 000 AU and a ∼ 45 000 AU and to be the main contributor at a ∼ 25 000 AU. Stellar perturbations make important contributions at all semi-major axes. On the basis of Hipparcos data, only a minority of the stars that may contribute to comet injections are detectable, since most stars have escaped to distances beyond the Hipparcos detection limit. For Gaia, on the other hand, a large majority of the perturbing stars will be both identifiable and measurable.

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Section: The Injected Cometssupporting

confidence: 92%

The last revolution of new comets: the role of stars and their detectability

Fouchard

Rickman

Froeschlé

et al. 2011

A&A

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“…However, we find that there are regions of parameter space where extrapolation of our results to the actual Centaur population is limited by the finite length of time of the simulation. Specifically, orbits of high eccentricity (ee0:8) with q in the Saturn-to-Neptune region have dynamical timescales too long for a 100 Myr integration to adequately probe (Wiegert & Tremaine 1999;Malyshkin & Tremaine 1999). On the other hand, for orbits of lowto-moderate eccentricities and perihelion distances in the Jupiter-to-Neptune range, the 100 Myr length of our integration is a factor $10 to 10 4 longer than the characteristic dynamical lifetimes.…”

Section: Are Centaur Dynamics Ergodic?mentioning

confidence: 93%

The Dynamics of Known Centaurs

2003

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We have numerically investigated the long-term dynamical behavior of known Centaurs. This class of objects is thought to constitute the transitional population between the Kuiper belt and the Jupiter-family comets (JFCs). In our study, we find that over their dynamical lifetimes these objects diffuse into the JFCs and other sinks, and they also make excursions into the scattered disk, but (not surprisingly) do not diffuse into the parameter space representing the main Kuiper belt. These Centaurs spend most of their dynamical lifetimes in orbits of eccentricity 0.2-0.6 and perihelion distance 12-30 AU. Their orbital evolution is characterized by frequent close encounters with the giant planets. Most of these Centaurs will escape from the solar system (or enter the Oort cloud), while a fraction will enter the JFC population and a few percent will impact a giant planet. Their median dynamical lifetime is 9 Myr, although there is a wide dispersion in lifetimes, ranging from less than 1 Myr to more than 100 Myr. We find the dynamical evolution of this sample of Centaurs to be less orderly than the planet-to-planet '' handoff '' described in previous investigations. We discuss the implications of our study for the spatial distribution of the Centaurs as a whole.

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“…The reduction of this ratio may be due to a modest fraction of the young + old population being daughters of the Kuiper belt/scattered disk. Additionally/alternatively, the ratio may be reduced as comets age by fading (Wiegert and Tremaine 1999), including the mass disruption of comets (Levison et al 2002). One sees in Fig.…”

Section: Distribution In the Tidal Characteristic Smentioning

confidence: 98%

“…The dominance of the galactic tide in making Oort cloud comets observable has been established on theoretical grounds (Heisler and Tremaine 1986). In contrast, the observational evidence for this dominance has not been compelling (Delsemme 1987, Matese and Whitman 1992, Wiegert and Tremaine 1999.…”

Section: Introductionmentioning

confidence: 99%

Perihelion evolution of observed new comets implies the dominance of the galactic tide in making Oort cloud comets discernable

Matese¹,

Lissauer²

2004

Icarus

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For an Oort cloud comet to be seen as a new comet, its perihelion must be moved from a point exterior to the loss cylinder boundary to a point interior to observable limits in a single orbit. The galactic tide can do this continuously, in a non-impulsive manner.Near-parabolic comets, with specific angular momentum H ∝ √ q, will most easily be made observable. Therefore, to reduce the perihelion distance, H must decrease. Since weakly perturbed comets are, in general, more numerous than strongly perturbed comets, we can anticipate that new comets made observable by a weak tidal torque will more likely be first observed when their slowly changing perihelion distances are approaching their minimum osculating values under the action of the tide, rather than receding from their minimum values.That is, defining ∆H tide as the vector change due to the galactic tidal torque during the prior orbit, and H obs as the observed vector, the sign S ≡ Sign(H obs · ∆H tide ) will more likely be −1 than +1 if a weak galactic tidal perturbation indeed dominates in making comets observable.Using comet data of the highest quality class (1A) for new comets (a > 10,000 AU), we find that 49 comets have S = −1 and 22 have S = +1. The binomial probability that as many or more would exhibit this characteristic if in fact S = ∓1 were equally likely is only 0.0009.This characteristic also persists in other long-period comet populations, lending support to the notion that they are dominated by comets recently arrived from the outer Oort Cloud. The preponderance of S = −1 also correlates with weakly perturbed (i.e., smaller semimajor axis) new comets in a statistically significant manner. This is strong evidence that the data are of sufficiently high quality and sufficiently free of observational selection effects to detect this unique imprint of the tide.

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The Evolution of Long-Period Comets

Cited by 174 publications

References 77 publications

The last revolution of new comets: the role of stars and their detectability

The last revolution of new comets: the role of stars and their detectability

The Dynamics of Known Centaurs

Perihelion evolution of observed new comets implies the dominance of the galactic tide in making Oort cloud comets discernable

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