On the population, physical decay and orbital distribution of Jupiter family comets: Numerical simulations

Abstract

We study the Jupiter family comet (JFC) population assumed to come from the Scattered Disk and transferred to the Jupiter's zone through gravitational interactions with the Jovian planets. We shall define as JFCs those with orbital periods P < 20 yr and Tisserand parameters in the range 2 < T K 3:1, while those comets coming from the same source, but that do not fulfill the previous criteria (mainly because they have periods P > 20 yr) will be called 'non-JFCs'. We performed a series of numerical simulations of fictitious comets with a purely dynamical model and also with a more complete dynamical-physical model that includes besides nongravitational forces, sublimation and splitting mechanisms. With the dynamical model, we obtain a poor match between the computed distributions of orbital elements and the observed ones. However with the inclusion of physical effects in the complete model we are able to obtain good fits to observations. The best fits are attained with four splitting models with a relative weak dependence on q, and a mass loss in every splitting event that is less when the frequency is high and vice versa. The mean lifetime of JFCs with radii R > 1 km and q < 1:5 AU is found to be of about 150-200 revolutions ($10 3 yrÞ. The total population of JFCs with radii R > 1 km within Jupiter's zone is found to be of 450 AE 50. Yet, the population of non-JFCs with radii R > 1 km in Jupiter-crossing orbits may be $4 times greater, thus leading to a whole population of JFCs + non-JFCs of $2250 AE 250. Most of these comets have perihelia close to Jupiter's orbit. On the other hand, very few non-JFCs reach the Earth's vicinity (perihelion distances q K 2 AU) which gives additional support to the idea that JFCs and Halley-type comets have different dynamical origins. Our model allows us to define the zones of the orbital element space in which we would expect to find a large number of JFCs. This is the first time, to our knowledge, that a physicodynamical model is presented that includes sublimation and different splitting laws. Our work helps to understand the role played by these erosion effects in the distribution of the orbital elements and lifetimes of JFCs.

An updated estimate of the number of Jupiter-family comets using a simple fading law

“…For JFCs with diameters between approximately 2 km and 10 km the slope γ ∼ 2 (Meech et al 2004;Snodgrass et al 2011), corresponding to α = 0.4. The number of JFCs with q < 2.5 AU and H T < 10.8 is then N vJFC = 294 +556 −235 , about three times higher than the number reported in and Di Sisto et al (2009). This is likely to be a lower limit because of the aforementioned incompleteness.…”

“…Since the JFCs originate in scattered disc Emel'yanenko et al 2004;Volk & Malhotra 2008;Di Sisto et al 2009;Brasser & Morbidelli 2013), we also update the inferred number of scattered disc objects (SDOs) by using the total number of active JFCs as a proxy. To compare our simulation with the observational data we need to have an observational catalogue of comets that is as complete as possible.…”

“…Fernández et al (2002) studied the evolution of JFCs in parallel to the above works, and reproduced the median dynamical lifetime and physical lifetimes reported in . Their work was superseded by that of Di Sisto et al (2009), who employed an elaborate splitting and fading mechanism to constrain the JFC population and reproduce the orbital element distributions. They conclude that the active lifetime is comparable to that found by and Fernández et al (2002) and that in steady state there are approximately 100 JFCs with diameter D > 2 km and q < 2.5 AU.…”

Giant comets and mass extinctions of life

“…As the time resolution of the record is degraded, it asymptotically approaches a random configuration which reproduces the observed number of crater pairs in only 0.2% of trials. latter arises from a combination of physical and dynamical evolution (Di Sisto et al 2009). For models in which impactors are the disintegration products of cascading fragmentation, α is probably somewhat smaller (Sekanina & Chodas 2007;Ishiguro et al 2009).…”

“…Defining the system of Jupiter family comets (JFCs) as having orbital periods P <20 yr and Tisserand criterion T <3, Di Sisto et al (2009) estimate a population of N =450 with perihelia q ≤2.5 au. For a mass distribution n(m) dm ∝ m −α dm in the radius range 1< R <10 km, the mass of the JFC system is then…”