BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Spinning up planetary bodies by pebble accretion								 - Rico Vi
 sser (Amsterdam)
DTSTART:20201110T130000Z
DTEND:20201110T140000Z
UID:TALK151885@talks.cam.ac.uk
CONTACT:Dr Annelies Mortier
DESCRIPTION:Most major planetary bodies in the Solar System rotate in the 
 same direction as their orbital motion: their spin is prograde. Theoretica
 l studies to explain the direction as well as the magnitude of the spin ve
 ctor have had mixed success. When the accreting building blocks are ∼ km
 -size planetesimals - as predicted by the classical model - the accretion 
 process is so symmetric that it cancels out prograde with retrograde spin 
 contributions\, rendering the net spin minute. For this reason\, the curre
 ntly-favored model for the origin of planetary rotation is the giant impac
 t model\, in which a single collision suffices to deliver a spin\, which m
 agnitude is close to the breakup rotation rate. However\, the giant impact
  model does not naturally explain the preference for prograde spin. Simila
 rly\, an increasing number of spin vector measurement of asteroids also sh
 ows that the spin vector of large (primordial) asteroids is not isotropic.
  Here\, we re-assess the viability of smaller particles to bestow planetar
 y bodies with a net spin\, focusing on the pebble accretion model in which
  gas drag and gravity join forces to accrete small particles at a large cr
 oss section. For simplicity\, our calculations have ignored certain import
 ant effects (e.g.\, collisions\, the back-reaction on the gas\, and format
 ion of atmospheres) and do not address how the eventual distribution of sp
 in vectors is obtained for which collisions and post-formation processes m
 ust have played a role to explain the scatter. Irrespective of these issue
 s\, pebble accretion is a viable mechanism to not only grow planetary bodi
 es\, but also to impart them with a significant spin.
LOCATION:ONLINE - Details to be sent by email
END:VEVENT
END:VCALENDAR