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: http://star.arm.ac.uk/~dja/papers/abs13EMP.html
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A model for the common origin of Jupiter Family and Halley Type comets V.V. Emel'yanenko, D.J. Asher and M.E. Bailey
Earth, Moon, & Planets, 110, 105-130 (2013)
Abstract:
A numerical simulation of the Oort cloud is used to explain the observed
orbital distributions and numbers of Jupiter-family (JF) and Halley-type (HT)
short-period (SP) comets. Comets are given initial orbits with perihelion
distances between 5 and 36 au, and evolve under planetary, stellar and
Galactic perturbations for 4.5 Gyr. This process leads to the formation of an
Oort cloud (which we define as the region of semimajor axes a > 1,000 au),
and to a flux of cometary bodies from the Oort cloud returning to the
planetary region at the present epoch. The results are consistent with the
dynamical characteristics of SP comets and other observed cometary
populations: the near-parabolic flux, Centaurs, and high-eccentricity
trans-Neptunian objects. To achieve this consistency with observations, the
model requires that the number of comets versus initial perihelion distance
is concentrated towards the outer planetary region. Moreover, the mean
physical lifetime of observable comets in the inner planetary region (q < 2.5
au) at the present epoch should be an increasing function of the comets'
initial perihelion distances. Virtually all observed HT comets and nearly
half of observed JF comets come from the Oort cloud, and initially (4.5 Gyr
ago) from orbits concentrated near the outer planetary region. Comets that
have been in the Oort cloud also return to the Centaur (5 < q < 28 au, a <
1,000 au) and near-Neptune high-eccentricity regions. Such objects with
perihelia near Neptune are hard to discover, but Centaurs with
characteristics predicted by the model (e.g. large semimajor axes, above 60
au, or high inclinations, above 40 deg) are increasingly being found by
observers. The model provides a unified picture for the origin of JF and HT
comets. It predicts that the mean physical lifetime of all comets in the
region q < 1.5 au is less than ~200 revolutions.