640 research outputs found
N-body Simulations of Satellite Formation around Giant Planets: Origin of Orbital Configuration of the Galilean Moons
As the number of discovered extrasolar planets has been increasing, diversity
of planetary systems requires studies of new formation scenarios. It is
important to study satellite formation in circumplanetary disks, which is often
viewed as analogous to formation of rocky planets in protoplanetary disks. We
investigated satellite formation from satellitesimals around giant planets
through N-body simulations that include gravitational interactions with a
circumplanetary gas disk. Our main aim is to reproduce the observable
properties of the Galilean satellites around Jupiter through numerical
simulations, as previous N-body simulations have not explained the origin of
the resonant configuration. We performed accretion simulations based on the
work of Sasaki et al. (2010), in which an inner cavity is added to the model of
Canup & Ward (2002, 2006). We found that several satellites are formed and
captured in mutual mean motion resonances outside the disk inner edge and are
stable after rapid disk gas dissipation, which explains the characteristics of
the Galilean satellites. In addition, owing to the existence of the disk edge,
a radial compositional gradient of the Galilean satellites can also be
reproduced. An additional objective of this study is to discuss orbital
properties of formed satellites for a wide range of conditions by considering
large uncertainties in model parameters. Through numerical experiments and
semianalytical arguments, we determined that if the inner edge of a disk is
introduced, a Galilean-like configuration in which several satellites are
captured into a 2:1 resonance outside the disk inner cavity is almost
universal. In fact, such a configuration is produced even for a massive disk
and rapid type I migration. This result implies the inevitability of a Galilean
satellite formation in addition to providing theoretical predictions for
extrasolar satellites.Comment: 20 pages, 9 figures, accepted for publication in Ap
The Effects of a Stellar Encounter on a Planetesimal Disk
We investigate the effects of a passing stellar encounter on a planetesimal
disk through analytical calculations and numerical simulations, and derive the
boundary radius () outside which planet formation is inhibited
by disruptive collisions with high relative velocities.Comment: 25 pages, 11 figures, included in 15 tex-files, 7 ps-files and 4
eps-file
Formation of dust-rich planetesimals from sublimated pebbles inside of the snow line
Content: For up to a few millions of years, pebbles must provide a
quasi-steady inflow of solids from the outer parts of protoplanetary disks to
their inner regions. Aims: We wish to understand how a significant fraction of
the pebbles grows into planetesimals instead of being lost to the host star.
Methods:We examined analytically how the inward flow of pebbles is affected by
the snow line and under which conditions dust-rich (rocky) planetesimals form.
When calculating the inward drift of solids that is due to gas drag, we
included the back-reaction of the gas to the motion of the solids. Results: We
show that in low-viscosity protoplanetary disks (with a monotonous surface
density similar to that of the minimum-mass solar nebula), the flow of pebbles
does not usually reach the required surface density to form planetesimals by
streaming instability. We show, however, that if the pebble-to-gas-mass flux
exceeds a critical value, no steady solution can be found for the solid-to-gas
ratio. This is particularly important for low-viscosity disks (alpha < 10^(-3))
where we show that inside of the snow line, silicate-dust grains ejected from
sublimating pebbles can accumulate, eventually leading to the formation of
dust-rich planetesimals directly by gravitational instability. Conclusions:
This formation of dust-rich planetesimals may occur for extended periods of
time, while the snow line sweeps from several au to inside of 1 au. The
rock-to-ice ratio may thus be globally significantly higher in planetesimals
and planets than in the central star.Comment: 5 pages, 3 figures; accepted for publication in Astronomy and
Astrophysic
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