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SUMMARY:Planet Formation By Chondrule Accretion
DTSTART;VALUE=DATE-TIME:20200513T093500Z
DTEND;VALUE=DATE-TIME:20200513T095500Z
DTSTAMP;VALUE=DATE-TIME:20240704T115619Z
UID:indico-contribution-46@meetings.aip.de
DESCRIPTION:Speakers: Åke Nordlund (Niels Bohr Institute\, Copenhagen)\nR
 ecently performed nested-grid\, high-resolution hydrodynamic and radiation
 -hydrodynamics simulations of gas and particle dynamics in the vicinity of
  Mars- to Earth-mass planetary embryos (Popovas et al 2018MNRAS.479.5136P 
 and 2019MNRAS.482L.107P) have provided quantitatively robust estimates of 
 accretion rates for planet embryos formed inside a pressure trap. The simu
 lations extended from the resolved surfaces of the embryos to several vert
 ical disk scale heights\, with a vertical dynamic range exceeding 1e5.  He
 ating due to the accretion of solids caused vigorous convective motions\, 
 however even convection driven by a nominal accretion rate  one Earth mass
  per Myr did not significantly alter the pebble accretion rate.   Ray-trac
 ing radiative transfer showed that rocky planet embryos embedded in protop
 lanetary disks can retain hot and light atmospheres throughout much of the
  evolution of the disks.\n\nImportantly\, the results showed that particle
 s larger than the chondrules ubiquitously observed  in meteorites are not 
 required to explain the accretion of rocky planets such as Earth and Mars 
 within the lifetime of the disk.  Due  to cancellation effects\, accretion
  rates of a given size particles are nearly independent of disk surface de
 nsity\, while proportional to the dust-to-gas ratio.  As a result\, accura
 te growth times for specified particle sizes may be estimated. For 0.3-1 m
 m size particles\, and assuming a dust-to-gas ratio of 1:100\, the growth 
 time from a small seed is ~1.5 million years for an Earth mass planet at 1
  AU and ~1 million years for a Mars mass planet at 1.5 AU. \n\nThe magnitu
 de and robustness of the accretion rate estimates hinges on the assumption
  of the embryo residing in a pressure trap.   A vertically projected dust 
 to gas ratio of 1:100 is thus a lower limit\, with continued trapping of m
 m-size particles expected to accelerate accretion.   This mechanism is the
 refore a prime candidate to explain rapid formation of rocky planets\, lea
 ving open only the question of by which mechanism the accretion is quenche
 d\, thus determining the final mass.\n\nI will discuss provocative scenari
 os where this question is resolved\, including implications for the format
 ion of gas dwarfs and gas giants.\n\nhttps://meetings.aip.de/event/1/contr
 ibutions/46/
LOCATION:Leibniz Institute for Astrophysics Potsdam (AIP) Lecture Hall
URL:https://meetings.aip.de/event/1/contributions/46/
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