HR: 11:05h
AN: P32A-04 [Abstracts]
TI: Accumulation of Giant Planet Atmospheres Around 5 -- 10 M$_{\oplus}$ Cores
AU: * Hubickyj, O
EM: hubickyj@pollack.arc.nasa.gov
AF: UCO/Lick Observatory, UC @ Santa Cruz, Santa Cruz, CA 95064
United States
AU: Bodenheimer, P
EM: peter@ucolick.org
AF: UCO/Lick Observatory, UC @ Santa Cruz, Santa Cruz, CA 95064
United States
AU: Lissauer, J J
EM: jlissauer@ringside.arc.nasa.gov
AF: NASA Ames Research Center, M. S. 245-3
, Moffett Field, CA 94035
United States
AB:
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\begin{document}
Observations of protoplanetary disks imply that gas giant planets form very
quickly ($\le$ 10 Myr). Recent interior models of Jupiter suggest smaller
core masses (0 -- 10 M$_\oplus$) than had been previously predicted
(10 to 30 M$_\oplus$).
We have computed evolutionary simulations of Jupiter based on the core
accretion model of gas giant planet formation where we vary the grain
opacity and the planetesimal surface density of the solar density of
the solar nebula. We also explore the implications of halting the
solid accretion at selected core mass values during the protoplanet's growth,
thus simulating the presence of a competing embryo.
The core accretion model states that a solid core is formed from the
accretion of planetesimals in the solar nebular followed by the capture
of a massive envelope from the solar nebula gas. Our simulations based
on this model (Pollack et al. 1996) have been successful in explaining
many features of the giant planets.
Our most recent results (Hubickyj et al. 2004) demonstrate that decreasing
the grain opacity reduces the formation time by more than half of that for
models computed with full interstellar grain opacity values. In fact, it
is the reduction of the grain opacity in the upper portion of the envelope
with T $<$ 500 K that governs the lowering of the formation time. Decreasing
the surface density of the planetesimals lowers the final core mass of the
protoplanet but increases the formation timescale. Finally, a core mass
cutoff results in the reduction of the time needed for a protoplanet to
evolve to the stage of runaway gas accretion provided the cutoff mass is not
too small. Our models show that with reasonable parameters it is possible
to form Jupiter by means of the core accretion process in 3 Myr or less.
\ref Hubickyj, O., P. Bodenheimer, & J. J. Lissauer 2004.
Accumulation of giant planet atmospheres around 5 -- 10
M$_{\oplus}$ cores. In preparation.
\ref Pollack J. B., O. Hubickyj, P. Bodenheimer, J. J. Lissauer,
M. Podolak, and Y. Greenzweig 1996. Formation of the giant
planets by concurrent accretion of solids and gas.
{\it Icarus \bf 124}, 62--85.
This work was supported in part by NASA grant NAG5--9661 and
NASA grant NAG 5--13285 from the Origins of Solar Systems Program.
\end{document}
DE: 6220 Jupiter
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting