BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Modeling the formation of giant planet cores - Levison\, H (Southw
 est Research Institute)
DTSTART:20090820T080000Z
DTEND:20090820T084000Z
UID:TALK19483@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:One of the most challenging problems we face in our understand
 ing of planet formation is how Jupiter and Saturn could have formed before
  the the solar nebula dispersed. The most popular model of giant planet fo
 rmation is the so-called 'core accretion' model. In this model a large pla
 netary embryo formed first\, mainly by two-body accretion. This is then fo
 llowed by a period of inflow of nebular gas directly onto the growing plan
 et. The core accretion model has an Achilles heel\, namely the very first 
 step. We have undertaken the most comprehensive study of this process to d
 ate. In this study we numerically integrate the orbits of a number of plan
 etary embryos embedded in a swarm of planetesimals. In these experiments w
 e have included a large number of physical processes that might enhance ac
 cretion. In particular\, we have included: 1) aerodynamic gas drag\, 2) co
 llisional damping between planetesimals\, 3) enhanced embryo cross-section
 s due to their atmospheres\, 4) planetesimal fragmentation\, and 5) planet
 esimal driven migration. We find that the gravitational interaction betwee
 n the embryos and the planetesimals lead to the wholesale redistribution o
 f material - regions are cleared of material and gaps open near the embryo
 s. Indeed\, in 90% of our simulations without fragmentation\, the region n
 ear that embryos is cleared of planetesimals before much growth can occur.
  The remaining 10%\, however\, the embryos undergo a burst of outward migr
 ation that significantly increases growth. On timescales of ~100\,000 year
 s\, the outer embryo can migrate ~6 AU and grow to roughly 30 Earth-masses
 . We also find that the inclusion of planetesimal fragmentation tends to i
 nhibit growth. 
LOCATION:Seminar Room 1 Newton Institute
END:VEVENT
END:VCALENDAR