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SUMMARY:A new exhibit in the planetary zoo: Hot\, rotating rocky planets -
  Simon Lock (Harvard)
DTSTART:20171005T103000Z
DTEND:20171005T113000Z
UID:TALK87821@talks.cam.ac.uk
CONTACT:Ed Gillen
DESCRIPTION:There is an incredible variation in the mass and radii of exop
 lanets. Generally\, the properties of exoplanets are inferred from interio
 r structure models that treat the bodies as cold\, differentiated and non-
 rotating. However\, exoplanets are not always in such states. Models of ac
 cretion predict that terrestrial bodies are formed with substantial angula
 r momentum. Rocky bodies can be hot because of proximity to their host sta
 rs or from giant impacts during accretion. We present a new code (HERCULES
 ) that solves for the equilibrium structure of rotating bodies as a series
  of concentric\, constant-density layers. The HERCULES code is an efficien
 t tool for calculating the structure of rotating exoplanets with realistic
  equations of state. Using HERCULES and a smoothed particle hydrodynamics 
 (SPH) code\, we show that hot\, rotating bodies display diverse morphologi
 es. In particular\, for rotating bodies there is a thermal limit at which 
 the rotational velocity at the equator intersects the Keplerian orbital ve
 locity. Beyond this corotation limit\, the body forms an extended\, contin
 uous structure with a corotating region and a disk-like region\, which we 
 have named a synestia. By analyzing SPH calculations of giant impacts and 
 N-body models of planet formation\, we show that typical rocky planets rea
 ch substantially vaporized states multiple times during accretion. For the
  expected mean angular momentum of growing planets\, most of these impact-
 generated states will exceed the corotation limit and be synestias. Hot\, 
 rotating structures can have a bulk density several times lower than an eq
 uivalent cold\, non-rotating body. The density inferred from observations 
 can also be inaccurate by a factor of a few\, depending on the orientation
  of an oblate body. In addition\, the range of structures for hot\, rotati
 ng bodies has significant implications for the differentiation\, cooling a
 nd internal dynamics of rocky bodies. Finally\, synestias lead to a new mo
 de of satellite formation that can explain the unique chemical relationshi
 p between the Earth and Moon.
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
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