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SUMMARY:Formation of Planets via Collisional Growth in Turbulent Disks - H
 iroshi Kobayashi (Nagoya)
DTSTART:20180621T103000Z
DTEND:20180621T113000Z
UID:TALK105052@talks.cam.ac.uk
CONTACT:Ed Gillen
DESCRIPTION:In the core accretion scenario\, gas giant planets are formed 
 form solid cores with several Earth masses via gas accretion.  We investig
 ate the formation of such cores via collisional growth from kilometer-size
 d planetesimals in turbulent disks.  The stirring by forming cores induces
  collisional fragmentation and surrounding planetesimals are ground down u
 ntil radial drift.  The core growth is therefore stalled by the depletion 
 of surrounding planetesiamls due to collisional fragmentation and radial d
 rift.  The collisional strength of planetesimals determines the planetesim
 al-depletion timescale\, which is prolonged for large planetesiamls.  The 
 size of planetesiamls around growing cores is determined by the planetesim
 al size distribution at the onset of runaway growth. Strong turbulence del
 ays the onset of runaway growth\, resulting in large planetesimals.  There
 fore\, the core mass evolution depends on turbulent parameter\,  alpha\; t
 he formation of cores massive enough without significant depletion of surr
 ounding planetesimals needs strong turbulence ( alpha > 0.001).  However\,
  the strong turbulence with a > 0.001 leads to a significant delay of the 
 onset of runaway growth and prevents the formation of massive cores within
  the disk lifetime.  The formation of cores massive enough within several 
 millions years therefore requires the several times enhancement of the sol
 id surface densities\, which is achieved in the inner disk $\\la 10$AU due
  to pile-up of drifting dust aggregates. In addition\, the collisional str
 ength QD* even for kilometer-sized or smaller bodies affects the growth of
  cores\; QD* > 10^7 erg/g for bodies < 1km is likely for this gas giant fo
 rmation.
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
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