The Centaur population

R. P. DI SISTO; A. BRUNINI

Buzios

Simposio; Symposium No 229 de la IAU: Asteroids, Comets, Meteors; 2005

IAU

 We analyse  here the  Centaur population as  a group of  objects withperihelion distances (q)  less than 30 AU, formed  by objects enteringthe planetary  zone from the  Scattered Disk (SD) and  objects leavingthe inner solar system. We  perform a numerical integration of 95 realscattered disk  objects (SDOs) extracted from the  Minor Planet Centerdatabase and 905 clones. We  consider them as massless particles underthe gravitational  influence of  the Sun and  the four  giant planets.The system  evolves for  4.5 Gy  or until a  particle collides  with aplanet,  reaches a  semimajor axis  a >  1000 AU  or enter  the regioninside Jupiter´s orbit (r<5.2 AU) where  it is considered to go over aJupiter Family Comet (JFC). At  this stage the objects evolve as JFCsup to reach again the Centaur zone contributing to this population butnow as a JFC. We evaluate also, the contribution of escaped Hildas andTrojan asteroids.  SDOs have in the  Centaur zone a mean  life time of72 My,  although this number fall  with a decrease of  q. After thisincursion, 22 %  of them enter the JFC zone and  return to the Centaurzone in  their way  to ejection  having there a  mean lifetime  of 1.2My. The mean lifetimes of escaped Hildas in that region is 2.3 My.  Wefound that  the greater contribution  to the Centaur  population comesfrom the  SD.  On  the other hand,  the majority  (more than 80  %) ofdiscovered  Centaurs have  q  < 20  AU.  Therefore we  guess that  theobserved Centaurs  are more likely  to be evolved objects  coming fromthe SD and there must be  lots of Centaurs not already discovered withlarge perihelion distances.