The Evolution of Jupiter Family Comets over 2000 Years (original) (raw)
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Astronomy & Astrophysics, 2012
We study the dynamical evolution of the near-Earth Jupiter family comets (NEJFCs) that came close to or crossed the Earth's orbit at the epoch of their discovery (perihelion distances q disc < 1.3 AU). We found a minimum in the time evolution of the mean perihelion distanceq of the NEJFCs at the discovery time of each comet (taken as t = 0) and a past-future asymmetry ofq in an interval -1000 yr, +1000 yr centred on t = 0, confirming previous results. The asymmetry indicates that there are more comets with greater q in the past than in the future. For comparison purposes, we also analysed the population of near-Earth asteroids in cometary orbits (defined as those with aphelion distances Q > 4.5 AU) and with absolute magnitudes H < 18. We found some remarkable differences in the dynamical evolution of both populations that argue against a common origin. To further analyse the dynamical evolution of NEJFCs, we integrated in time a large sample of fictitious comets, cloned from the observed NEJFCs, over a 20 000 yr time interval and started the integration before the comet's discovery time, when it had a perihelion distance q > 2 AU. By assuming that NEJFCs are mostly discovered when they decrease their perihelion distances below a certain threshold q thre = 1.05 AU for the first time during their evolution, we were able to reproduce the main features of the observedq evolution in the interval [-1000, 1000] yr with respect to the discovery time. Our best fits indicate that ∼40% of the population of NEJFCs would be composed of young, fresh comets that entered the region q < 2 AU a few hundred years before decreasing their perihelion distances below q thre , while ∼60% would be composed of older, more evolved comets, discovered after spending at least ∼3000 yr in the q < 2 AU region before their perihelion distances drop below q thre . As a byproduct, we put some constraints on the physical lifetime τ phys of NEJFCs in the q < 2 AU region. We found a lower limit of a few hundreds of revolutions and an upper limit of about 10 000-12 000 yr, or about 1600-2000 revolutions, somewhat longer than some previous estimates. These constraints are consistent with other estimates of τ phys , based either on mass loss (sublimation, outbursts, splittings) or on the extinction rate of Jupiter family comets (JFCs).
The persistent activity of Jupiter-family comets at 3–7AU
Icarus, 2013
We present an analysis of comet activity based on the Spitzer Space Telescope component of the Survey of the Ensemble Physical Properties of Cometary Nuclei. We show that the survey is well suited to measuring the activity of Jupiter-family comets at 3-7 AU from the Sun. Dust was detected in 33 of 89 targets (37 ± 6%), and we conclude that 21 comets (24 ± 5%) have morphologies that suggest ongoing or recent cometary activity. Our dust detections are sensitivity limited, therefore our measured activity rate is necessarily a lower limit. All comets with small perihelion distances (q < 1.8 AU) are inactive in our survey, and the active comets in our sample are strongly biased to post-perihelion epochs. We introduce the quantity f ρ, intended to be a thermal emission counterpart to the often reported Af ρ, and find that the comets with large perihelion distances likely have greater dust production rates than other comets in our survey at 3-7 AU from the Sun, indicating a bias in the discovered Jupiter-family comet population. By examining the orbital history of our survey sample, we suggest that comets perturbed to smaller perihelion distances in the past 150 yr are more likely to be active, but more study on this effect is needed.
First Results of the Integration of Motion of Short-Period Comets Over 800 Years
Astrophysics and Space Science Library, 1985
All the known short-period comets have been followed by numerical integration over a time span of 821 years, from 1585 to 2406. A preliminary survey of the results of these integrations has shown some interesting features, which become recognizable thanks to the length of the time interval covered, not negligible if compared with the typical evolutionary time scale of comets moving in short-period orbits. Interesting phenomena that have been recognized include: (1) captures from, or ejections into, very elongated ellipses, with perihelia of the parking orbits close to the orbit of Jupiter and aphelia within or beyond the region of outer planets; (2) passages of comets from the control of Saturn to that of Jupiter; (3) orbital evolutions controlled mainly by Saturn; (4) librations of comets around low-order resonances; (5) repeated close approaches of comets to Jupiter, often with the comet being captured as a temporary satellite; (6) an almost perfect coincidence of two comet orbits just before a close approach to Jupiter, suggesting their genetic relationship.
Dynamical Evolution of Ecliptic Comets
Comets II, 2004
In this chapter, we review the enormous progress that has been made in our understanding of the dynamical evolution of these bodies. We begin by reviewing the evidence that Jupiter-family comets (JFCs; those with 2 < T < 3) form a dynamically distinct class of comets that originate in a flattened disk beyond Neptune. We present a model for the distribution of comets throughout the JFC and Centaur regions that is consistent with current observations, although further observations and numerical simulations in the Centaur region are called for. We then discuss dynamical results (since confirmed by observations) that a significant amount of material that was scattered by Neptune during the early stages of planet formation could persist today in the form of a "scattered disk" of bodies with highly eccentric orbits beyond Neptune. We describe the dynamical mechanisms believed responsible for the longevity of the surviving bodies and argue that if objects in the Kuiper belt and scattered disk have similar size distributions, then the scattered disk is likely to be the primary source of JFCs and Centaurs. Finally, we describe the importance of understanding the ecliptic comet population for the purposes of determining impact rates on the satellites of the giant planets and of age determinations of the satellite surfaces. We present tables of impact rates based on the best currently available analyses. Further refinements of these rates and age determinations await better observations of the Centaur population (including its size distribution), as well as a better understanding of the formation and early dynamical evolution of the outer solar system.
The Persistent Activity of Jupiter-Family Comets at 3 to 7 AU
2013
We present an analysis of comet activity based on the Spitzer Space Telescope component of the Survey of the Ensemble Physical Properties of Cometary Nuclei. We show that the survey is well suited to measuring the activity of Jupiter-family comets at 3-7 AU from the Sun. Dust was detected in 33 of 89 targets (37 +/- 6%), and we conclude that 21 comets (24 +/- 5%) have morphologies that suggest ongoing or recent cometary activity. Our dust detections are sensitivity limited, therefore our measured activity rate is necessarily a lower limit. All comets with small perihelion distances (q < 1.8 AU) are inactive in our survey, and the active comets in our sample are strongly biased to post-perihelion epochs. We introduce the quantity epsilon-f-rho, intended to be a thermal emission counterpart to the often reported A-f-rho, and find that the comets with large perihelion distances likely have greater dust production rates than other comets in our survey at 3-7 AU from the Sun, indicati...
The paper presents the study of the dependence between photometric parameters of selected short-period comets of the Jupiter family and the activity of the Sun. As a quantity of solar activity, we used the sunspot area, the Wolf number, the annual mean solar radio flux, the solar flare index (full disk), and the annual mean AA-index solar activity. To study the correlation between cometary and solar activity the Dobrovolsky method was used. It has been found no direct correlation between the absolute stellar magnitude and the photometric parameter of comets with individual parameters of solar activity. Moreover, the correlation coefficients show that some comets are not associated with solar activity.
Astronomy and Astrophysics Supplement Series, 1996
The results from the second campaign of the search for comets in the vicinity of Jupiter are presented. As in the previous campaign, we find no comets. This result is used to calculate upper limits on the size of the Jupiter family population of comets. The numbers found are the same as in the previous campaign, but have the advantage that the lack of complete discovery at the limiting magnitude is taken into account. We find that for comets brighter than nuclear B magnitude 14 (corresponding to a radius of 8 km) the population consist of up to 210 members. This value is extrapolated to fainter magnitudes (smaller sizes).
The population, magnitudes, and sizes of Jupiter family comets
Astronomy & Astrophysics, 1999
We analyze the sample of measured nuclear magnitudes of the observed Jupiter family (JF) comets (taken as those with orbital periods P < 20 years and Tisserand parameters T > 2). We find a tendency of the measured nuclear magnitudes to be fainter as JF comets are observed with CCD detectors attached to medium-and large-size telescopes (e.g. Spacewatch Telescope). However, a few JF comets observed very far from the Sun (4-7 AU) show a wide dispersion of their derived absolute nuclear magnitudes which suggests that either these JF comets keep active all along the orbit, so the reported unusually bright distant magnitudes were strongly contaminated by a coma, or some of the measured "nuclear magnitudes" were grossly overestimated (i.e. their brightness underestimated).
Jupiter family comets in near-Earth orbits: Are some of them interlopers from the asteroid belt?
Planetary and Space Science, 2015
We analyze a sample of 58 Jupiter family comets (JFCs) in near-Earth orbits, defined as those whose perihelion distances at the time of discovery were q 1.3 disc < au. In our definition JFCs have Tisserand parameters T 2 3 < < and orbital periods P 20 < yr. We integrated the orbits of these objects, plus 50 clones for each one of them, for 10 4 yr in the past and in the future. We find that most of them move on highly unstable orbits, having fallen in their current near-Earth orbits in the recent past, going from less than one hundred years to a few thousands years. They experience frequent close encounters with Jupiter down to distances 0.1 ≲ au. This is the expected behavior for comets whose limited physical lifetimes in the near-Earth region make them unlikely to survive there for more than about a few hundred revolutions. In this sense the orbits of most JFCs are typically "cometary", and they should be regarded as newcomers in the near-Earth region. Yet, a minor fraction of JFCs (less than about one third) are found to move on stable orbits for the past 10 4 ∼ yr, and in some cases are found to continue to be stable at 5 10 4 × yr in the past. They also avoid very close encounters with Jupiter. Their orbital behavior is very similar to that of NEAs in cometary orbits. While "typical" JFCs in unstable orbits probably come from the trans-Neptunian region, the minor group of JFCs in asteroidal orbits may come from the main asteroid belt, like the NEAs. The asteroidal JFCs may have a more consolidated structure and a higher mineral content than that of comets coming from the trans-Neptunian belt or the Oort cloud, which could explain their much longer physical lifetimes in the near-Earth region. In particular, we mention comets 66P/du Toit, 162P/Siding Spring, 169P/NEAT, 182P/LONEOS, 189P/NEAT, 249P/LINEAR, 300P/Catalina, and P/2003 T12 (SOHO) as the most likely candidates to have an origin in the main asteroid belt. Another interesting case is 207P/NEAT, which stays near the 3:2 inner mean motion resonance with Jupiter, possibly evolving from the Hilda asteroid zone.
Dust environment and dynamical history of a sample of short-period comets
Astronomy & Astrophysics, 2014
Aims. In this work, we present an extended study of the dust environment of a sample of short period comets and their dynamical history. With this aim, we characterized the dust tails when the comets are active, and we made a statistical study to determine their dynamical evolution. The targets selected were 22P/Kopff, 30P/Reinmuth 1, 78P/Gehrels 2, 115P/Maury, 118P/Shoemaker-Levy 4, 123P/West-Hartley, 157P/Tritton, 185/Petriew, and P/2011 W2 (Rinner). Methods. We use two different observational data: a set of images taken at the Observatorio de Sierra Nevada and the A f ρ curves provided by the amateur astronomical association Cometas-Obs. To model these observations, we use our Monte Carlo dust tail code. From this analysis, we derive the dust parameters, which best describe the dust environment: dust loss rates, ejection velocities, and size distribution of particles. On the other hand, we use a numerical integrator to study the dynamical history of the comets, which allows us to determine with a 90% of confidence level the time spent by these objects in the region of Jupiter Family Comets. Results. From the Monte Carlo dust tail code, we derived three categories attending to the amount of dust emitted: Weakly active (115P, 157P, and Rinner), moderately active (30P, 123P, and 185P), and highly active (22P, 78P, and 118P). The dynamical studies showed that the comets of this sample are young in the Jupiter Family region, where the youngest ones are 22P (∼ 100 yr), 78P (∼ 500 yr), and 118P (∼ 600 yr). The study points to a certain correlation between comet activity and time spent in the Jupiter Family region, although this trend is not always fulfilled. The largest particle sizes are not tightly constrained, so that the total dust mass derived should be regarded as lower limits.