Gal Sarid

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DYNAMICAL AND THERMAL PATHWAYS IN THE EVOLUTION OF CENTAUR OBJECTS.   
Gal Sarid, NASA Astrobiology Institute and Institute for Astronomy, University of Hawai’i, Honolulu, HI, 
galahead@ifa.hawaii.edu 
 
 
Introduction: The structural and thermal evolution 
of small Solar system bodies may be strongly 
dependent on their dynamical history and environment. 
Objects that occupy planet-crossing orbits are more 
prone to gravitational perturbations that de-stabilize 
their orbits. Such are the Centuars, which are 
conjectured to be a transient and intermediate 
population, between the relatively stable trans-
Neptunian objects (TNOs) and the short-lived Jupiter 
family Comets (JFCs) [1].  
Most known Centuars have an asteroid-like 
dormant appearance. However, several objects have 
been known to exhibit cometary-like emission activity 
at various times [2]. This kind of activity, at such large 
heliocentric distances, is peculiar and provides a good 
reason for modeling their thermal and structural 
evolution. The dynamical role, as a transition phase 
between the TNOs and JFCs, may indicate that these 
objects experience intermediate levels of internal 
processing, at different periods of hteir lives.  
A careful examination of the evolution of several of 
the best-characterized Centaur objects, both in orbital 
and physical parameters, can help categorize the 
different states and origin and evolution scenarios in 
the outer Solar system.  
 
Modeling Issues:  We apply our well-tested and 
robust thermal code to the modeling of several specific 
objects [3,4]. We examine the effect of various initial 
conditions on the thermal evolution of objects on  
different unstable orbits. For this purpose, we set
different scenarios for the succession of Centaur origin 
and emplacement – either as ‘a chip of the old block’ 
of larger TNOs [5], which scattered inwards, or as a 
‘rolling stone’ from out beyond Neptune, which 
diffused inwards.  
The dynamical state of these specific objects is 
examined through N-body intergrations, utilizing the 
SWIFT integration package [6]. This is achieved by 
using many clones of specific objects, where the initial 
conditions for the clones are centered In the phase 
space, around known orbital elements. The orbits of 
such objects are highly chaotic and as such, 
characterizing their orbital stability reveals some of the 
intricate dynamical states present in the current 
configuration of the outer Solar system.     
 
 
Results: Here we present some results and 
considerations, regarding the link between dynamical 
and thermal evolution of Centaurs. Profiles of 
temperature, structure and composition are calculated 
for the different objects, which represent slightly 
varying dynamical groups, and for different orbits of 
the same object, which represent specific orbital 
evolution pathways. This has an influence on the 
internal stratified structure, through an adapting 
thermal response of the nucleus.  
The determination of the dynamical groups is 
achieved through statistical analysis of the results of 
our orbital integrations. Although previous studies 
showed that the intrinsic Centaur population is highly 
dispersed in orbital configurations [7], the statistics of 
large clone samples of specific objects can yield 
valuable information about their current states and 
future fates. Specifically, and with greater importance 
to the thermal modeling, we focus on the dynamical 
lifetimes and mean orbital elements. The latter are
considered during the relatively stable and non-
diffusive phase of orbital evolution.  
 
Acknowledgements: G. S. would like to acknowledge 
the support of the National Aeronautics and Space 
Administration through the NASA Astrobiology Institute 
under Cooperative Agreement No. NNA08DA77A issued 
through the Office of Space Science. Any opinions, fi dings, 
and conclusions or recommendations expressed in this article 
(or report, material, etc) are those of the author(s) and do not 
necessarily reflect the views of the National Aeronautics and 
Space Administration. 
 
References: [1] Duncan M, Levison H. and Dones L. 
(2004) in Comets II, edited by Festou M., Keller H. U. 
and Weaver H. A., 193-204. [2] Jewitt D. (2009) AJ, 
137, 4296-4312. [3] Prialnik D., Sarid G., Rosenberg 
E. D. and Merk R. (2008) Sp. Sci. Rev., 138, 147-164.       
[4] Sarid G. and Prialnik D. (2011) Icarus, under 
revision. [5] Sarid G. and Prialnik D. (2009) M&PS, 
44, 1905-1916. [6] Levison H. F. and Duncan M. J. 
(1994) Icarus, 108, 18-36. [7] Tiscareno M. S. and 
Malhotra R. (2003) AJ, 126, 3122-3131. [8] Guilbert 
A., Barucci M. A., Brunetto R., Delsanti A., Merlin F., 
Alvarez-Candal A., Fornasier S., de Bergg C. and Sarid 
G. (2009) A&A, 501, 777-784.    
 


DYNAMICAL AND THERMAL PATHWAYS IN THE EVOLUTION OF CENTAUR OBJECTS

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DYNAMICAL AND THERMAL PATHWAYS IN THE EVOLUTION OF CENTAUR OBJECTS

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