127 research outputs found
On the Formation of Gas Giant Planets on Wide Orbits
A new suite of three dimensional radiative, gravitational hydrodynamical
models is used to show that gas giant planets are unlikely to form by the disk
instability mechanism at distances of ~100 AU to ~200 AU from young stars. A
similar result seems to hold for the core accretion mechanism. These results
appear to be consistent with the paucity of detections of gas giant planets on
wide orbits by infrared imaging surveys, and also imply that if the object
orbiting GQ Lupus is a gas giant planet, it most likely did not form at a
separation of ~100 AU. Instead, a wide planet around GQ Lup must have undergone
a close encounter with a third body that tossed the planet outward to its
present distance from its protostar. If it exists, the third body may be
detectable by NASA's Space Interferometry Mission.Comment: 13 pages, 4 figures. in press, ApJ Letter
On Pressure Gradients and Rapid Migration of Solids in an Inhomogeneous Solar Nebula
We study the motions of small solids, ranging from micron-sized dust grains
to 100-m objects, in the vicinity of a local density enhancement of an
isothermal gaseous solar nebula. Being interested in possible application of
the results to the formation of clumps and spiral arms in a circumstellar disk,
we numerically integrate the equations of motion of such solids and study their
migration for different values of their sizes and masses and also for different
physical properties of the gas, such as its density and temperature. We show
that, considering the drag force of the gas and also the gravitational
attraction of the nebula, it is possible for solids, within a certain range of
size and mass, to migrate rapidly (i.e. within ~1000 years) toward the location
of a local maximum density where collisions and coagulation may result in an
accelerated rate of planetesimal formation.Comment: 20 pages, 7 figures, submitted for publicatio
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