Browsing by Subject "planets and satellites: dynamical evolution and stability"

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Circumbinary Planet Formation In The Kepler-16 System. II. A Toy Model For In Situ Planet Formation Within A Debris Belt
(2014-07) Meschiari, Stefano; Meschiari, Stefano
Recent simulations have shown that the formation of planets in circumbinary configurations (such as those recently discovered by Kepler) is dramatically hindered at the planetesimal accretion stage. The combined action of the binary and the protoplanetary disk acts to raise impact velocities between kilometer-sized planetesimals beyond their destruction threshold, halting planet formation within at least 10 AU from the binary. It has been proposed that a primordial population of "large" planetesimals (100 km or more in size), as produced by turbulent concentration mechanisms, would be able to bypass this bottleneck; however, it is not clear whether these processes are viable in the highly perturbed circumbinary environments. We perform two-dimensional hydrodynamical and N-body simulations to show that kilometer-sized planetesimals and collisional debris can drift and be trapped in a belt close to the central binary. Within this belt, planetesimals could initially grow by accreting debris, ultimately becoming "indestructible" seeds that can accrete other planetesimals in situ despite the large impact speeds. We find that large, indestructible planetesimals can be formed close to the central binary within 10(5) yr, therefore showing that even a primordial population of "small" planetesimals can feasibly form a planet.
Planet Formation in Circumbinary Configurations: Turbulence Inhibits Planetesimal Accretion
(2012-12) Meschiari, Stefano; Meschiari, Stefano
The existence of planets born in environments highly perturbed by a stellar companion represents a major challenge to the paradigm of planet Formation. In numerical simulations, the presence of a close binary companion stirs up the relative velocity between planetesimals, which is fundamental in determining the balance between accretion and erosion. However, the recent discovery of circumbinary planets by Kepler establishes that planet Formation in binary systems is clearly viable. We perform N-body simulations of planetesimals embedded in a protoplanetary disk, where planetesimal phasing is frustrated by the presence of stochastic torques, modeling the expected perturbations of turbulence driven by the magnetorotational instability. We examine perturbation amplitudes relevant to dead zones in the midplane (conducive to planet Formation in single stars), and find that planetesimal accretion can be inhibited even in the outer disk (4-10 AU) far from the central binary, a location previously thought to be a plausible starting point for the Formation of circumbinary planets.
Transit Timing Observations From Kepler. IV. Confirmation Of Four Multiple-Planet Systems By Simple Physical Models
(2012-05) Fabrycky, Daniel C.; Ford, Eric B.; Steffen, Jason H.; Rowe, Jason F.; Carter, Joshua A.; Moorhead, Althea V.; Batalha, Natalie M.; Borucki, William J.; Bryson, Steve; Buchhave, Lars A.; Christiansen, Jessie L.; Ciardi, David R.; Cochran, William D.; Endl, Michael; Fanelli, Michael N.; Fischer, Debra; Fressin, Francois; Geary, John; Haas, Michael R.; Hall, Jennifer R.; Holman, Matthew J.; Jenkins, Jon M.; Koch, David G.; Latham, David W.; Li, Jie; Lissauer, Jack J.; Lucas, Philip; Marcy, Geoffrey W.; Mazeh, Tsevi; McCauliff, Sean; Quinn, Samuel; Ragozzine, Darin; Sasselov, Dimitar; Shporer, Avi; Cochran, William D.; Endl, Michael
Eighty planetary systems of two or more planets are known to orbit stars other than the Sun. For most, the data can be sufficiently explained by non-interacting Keplerian orbits, so the dynamical interactions of these systems have not been observed. Here we present four sets of light curves from the Kepler spacecraft, each which of shows multiple planets transiting the same star. Departure of the timing of these transits from strict periodicity indicates that the planets are perturbing each other: the observed timing variations match the forcing frequency of the other planet. This confirms that these objects are in the same system. Next we limit their masses to the planetary regime by requiring the system remain stable for astronomical timescales. Finally, we report dynamical fits to the transit times, yielding possible values for the planets' masses and eccentricities. As the timespan of timing data increases, dynamical fits may allow detailed constraints on the systems' architectures, even in cases for which high-precision Doppler follow-up is impractical.