604 Encyclopedia of the Solar System
It has been argued that the explanation of the most
important observed properties of the trans-Neptunian
population require a “cocktail” with three ingredients:
(1) a truncated planetesimal disk; (2) a dense galactic envi-
ronment, favoring stellar passages at about 1000 AU from
the Sun; and (3) the outward migration of Neptune with,
presumably, a phase of large eccentricity of the planetary
orbits. Some problems still remain open, and the details
of some mechanisms have still to be understood, but the
basic composition of the cocktail appears quite secure. This
is a big step forward with respect to our understanding of
solar system formation, before the discovery of the Kuiper
Belt.
What is next? The upcoming generation of telescopic
surveys will probably increase by another order of mag-
nitude the number of discovered trans-Neptunian objects
with good orbits within a decade. Thus, in the third edition
of the encyclopedia, we will probably have a different story
to tell. It is unlikely that our view will totally change with
the new discoveries (or at least we hope so!), but certainly
there will be surprises. We are anxious to know more pre-
cisely the absolute magnitude distributions of the various
subpopulations of the Kuiper Belt, their color properties,
the real nature of the outer edge and its exact location,
the orbital distribution of the extended scattered disk. This
information will allow us to refine the scenarios outlined
earlier, possibly to reject some and design new ones, in an
attempt to read with less uncertainty the history of our solar
system that is written out there.
Bibliography
Bernstein, G. M., Trilling, D. E., Allen, R. L., Brown, M. E.,
Holman, M., and Malhotra, R. (2004). The size distribution of
trans-Neptunian bodies.Astron. J. 128 , 1364–1390.
Brown M. (2001). The inclination distribution of the Kuiper
Belt.Astron. J. 121 , 2804–2814.
Gomes R. S. (2003). The origin of the Kuiper Belt high incli-
nation population.Icarus 161 , 404–418.
Gomes, R., Levison, H. F., Tsiganis, K., and Morbidelli, A.
(2005). Origin of the cataclysmic Late Heavy Bombardment pe-
riod of the terrestrial planets.Nature 435 , 466–469.
Levison H. F., and Stern S. A. (2001). On the size dependence
of the inclination distribution of the Main Kuiper Belt.Astron. J.
121 , 1730–1735.
Levison, H. F., and Morbidelli, A. (2003). The formation of the
Kuiper Belt by the outward transport of bodies during Neptune’s
migration.Nature 426 , 419–421.
Malhotra R. (1995). The origin of Pluto’s orbit: Implications
for the solar system beyond Neptune.Astron. J. 110 , 420–432.
Morbidelli, A., Brown, M.E., and Levison, H. F. (2003). The
Kuiper Belt and its primordial sculpting.Earth Moon and Planets
92 , 1–27.
Morbidelli, A., and Levison, H. F. (2004). Scenarios for the
origin of the orbits of the trans-Neptunian objects 2000 CR 105 and
2003 VB 12 (Sedna).Astron. J. 128 , 2564–2576.
Trujillo C. A., and Brown M. E. (2001). The radial distribution
of the Kuiper Belt.Astrophys. J. 554 , 95–98.
Trujillo C. A., and Brown M. E. (2002). A correlation between
inclination and color in the classical Kuiper Belt.Astroph. J. 566 ,
125–128.