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SUMMARY:Collisional growth of planetesimals - Andrew Shannon (Institute of
  Astronomy\, Cambridge)
DTSTART:20130129T130000Z
DTEND:20130129T140000Z
UID:TALK42535@talks.cam.ac.uk
CONTACT:Jérôme Guilet
DESCRIPTION:Traditional models of planetesimal growth begin with kilometre
  sized bodies\, which grow by pairwise collisions.  The fastest growing bo
 dies run away from the distribution\, which causes larger planetesimals (1
 00-1000 km) to form with low (less than 1 percent) efficiency. This low ef
 ficiency has been regarded as favourable\, as the mass of the asteroid and
  Kuiper belts is similarly lower than the expectations from the minimum ma
 ss solar nebula.\n\nHowever\, new results suggest that the Kuiper belt reg
 ion could never have had much more mass than it does today\, and that extr
 asolar debris disks contain enough mass in larger (100~1000 km) bodies tha
 t they must have formed with high efficiency.  We revisit growth starting 
 from a kilometre\, and show it always has low efficiency.  We consider an 
 alternate case\, where planetesimals grow by accreting very small (cm) obj
 ects\, and show that collisional cooling among the cm grains changes the c
 haracter of growth\, allowing it to proceed with high efficiency\, satisfy
 ing the observational demands of the Kuiper belt and extrasolar debris dis
 ks.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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