416 research outputs found
Dynamics, Origin, and Activation of Main Belt Comets
The discovery of Main Belt Comets (MBCs) has raised many questions regarding
the origin and activation mechanism of these objects. Results of a study of the
dynamics of these bodies suggest that MBCs were formed in-situ as the remnants
of the break-up of large icy asteroids. Simulations show that similar to the
asteroids in the main belt, MBCs with orbital eccentricities smaller than 0.2
and inclinations lower than 25 degrees have stable orbits implying that many
MBCs with initially larger eccentricities and inclinations might have been
scattered to other regions of the asteroid belt. Among scattered MBCs,
approximately 20 percent reach the region of terrestrial planets where they
might have contributed to the accumulation of water on Earth. Simulations also
show that collisions among MBCs and small objects could have played an
important role in triggering the cometary activity of these bodies. Such
collisions might have exposed sub-surface water ice which sublimated and
created thin atmospheres and tails around MBCs. This paper discusses the
results of numerical studies of the dynamics of MBCs and their implications for
the origin of these objects. The results of a large numerical modeling of the
collisions of m-sized bodies with km-sized asteroids in the outer part of the
asteroid belt are also presented and the viability of the collision-triggering
activation scenario is discussed.Comment: 9 pages, 4 figures, to appear in the proceedings of IAU Symposium
263: Icy Bodies of the Solar System (Eds. D. Lazzaro, D. Prialnik, o. Schulz
and J.A. Fernandez), Cambridge Univ. Pres
On the Dynamical Stability of Gamma Cephei, an S-Type Binary Planetary System
Precision radial velocity measurements of the Gamma Cephei (HR8974) binary
system suggest the existence of a planetary companion with a minimum mass of
1.7 Jupiter-mass on an elliptical orbit with a ~2.14 AU semimajor axis and 0.12
eccentricity (hatzes et al. 2003). I present in this paper a summary of the
results of an extensive numerical study of the orbital stability of this
three-body system for different values of the semimajor axis and orbital
eccentricity of the binary, and also the orbital inclination of the planet.
Numerical integrations indicate that the system is stable for the planet's
orbital inclination ranging from 0 to 60 degrees, and for the binary's orbital
eccentricity less than 0.5. The results also indicate that for large values of
the inclination, the system may be locked in a Kozai resonance.Comment: 5 pages, 3 figures, to appear in the proceedings of "The Search For
Other Worlds." The 14th Annual October Astrophysics Conference in Maryland.
Eds. De. Deming and S. Holt (PASP Style
On the Growth of Dust Particles in a Non-Uniform Solar Nebula
A summary of the results of a numerical study of the growth of solid
particles in the vicinity of an azimuthally symmetric density enhancement of a
protostellar disk are presented. The effects of gas drag and pressure gradients
on the rate of growth of dust particles and their settling on the midplane of
the nebula are also discussed.Comment: 4 pages, 2 figures, in the proceedings of "The Search For Other
Worlds." The 14th Annual October Astrophysics Conference in Maryland. Eds. D.
Deming and S. Hol
Partial Averaging Near a Resonance in Planetary Dynamics
Following the general numerical analysis of Melita and Woolfson (1996), I
showed in a recent paper that a restricted, planar, circular planetary system
consisting of Sun, Jupiter and Saturn would be captured in a near (2:1)
resonance when one would allow for frictional dissipation due to interplanetary
medium (Haghighipour, 1998). In order to analytically explain this resonance
phenomenon, the method of partial averaging near a resonance was utilized and
the dynamics of the first-order partially averaged system at resonance was
studied. Although in this manner, the finding that resonance lock occurs for
all initial relative positions of Jupiter and Saturn was confirmed, the
first-order partially averaged system at resonance did not provide a complete
picture of the evolutionary dynamics of the system and the similarity between
the dynamical behavior of the averaged system and the main planetary system
held only for short time intervals. To overcome these limitations, the method
of partial averaging near a resonance is extended to the second order of
perturbation in this paper and a complete picture of dynamical behavior of the
system at resonance is presented. I show in this study that the dynamics of the
second-order partially averaged system at resonance resembles the dynamical
evolution of the main system during the resonance lock in general, and I
present analytical explanations for the evolution of the orbital elements of
the main system while captured in resonance.Comment: Plain TeX, 21 Pages, 6 Figures, Submitted to
Celest.Mech.Dynamic.Astr
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