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Complex Planetary Systems

Volume 9 - Issue S310 - July 2014
Contents

Page 4 of 4

Contributed Papers

  • Reversing Type I Migration in Gap Shadows

  • Hannah Jang-Condell
  • Published online by Cambridge University Press:
    05 January 2015, pp. 214-215
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  • Type I migration refers to the radial drift of a sub-Jupiter mass planet resulting from tidal interactions with a protoplanetary disk. It results in the rapid inward migration of small planets and planet cores through the disk. Type I migration is so rapid compared to disk dissipation time scales that explaining distant planets, such as the HR 8799 planets and Jupiter itself, is problematic because their growing cores should have been lost. Here, we present a scenario for solving the Type I migration problem. As a planet grows in mass, its Type I migration rate should increase, assuming that disk properties are not significantly altered by the forming planet. But a growing planet clears some, but not all, material from its orbital path, creating a partial gap in the disk. The trough of a partially cleared gap such as this is shadowed from stellar illumination while the far side of the gap is illuminated. Since stellar irradiation is the primary heat source of passively accreting protoplanetary disks, gap self-shadowing can significantly change the local temperature profile. This change to the local temperature gradient can significantly slow, or even reverse Type I migration.

  • Planet Formation in Close Binaries

  • Hannah Jang-Condell
  • Published online by Cambridge University Press:
    05 January 2015, pp. 216-217
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  • Several exoplanets have been discovered in close binaries (a < 30 AU) to date.

    The fact that planets can form in these dynamically challenging environments says that planet formation must be a robust process. Disks in these systems should be tidally truncated to within a few AU, so if they form in situ, the efficiency of planet formation must be high. While the dynamical capture of planets is also a possibility, the probability of these interactions is low, so in situ formation is the more plausible explanation. I examine the truncation of protoplanetary disks in close binary stars, studying how the disk mass is affected as it evolves from higher accretion rates to lower rates. In the gamma Cephei system, a protoplanetary disk around the primary star should be truncated to within a few AU, but enough mass still remains for planets to form. However, if the semimajor axis of the binary is too small or its eccentricity is too high, such as in HD 188753, the disk will have too little mass for planet formation to occur. I present a way to characterize the feasibility of planet formation based on binary orbital parameters such as stellar mass, companion mass, eccentricity and semi-major axis. Using this measure, we can quantify the robustness of planet formation in close binaries and better understand the overall efficiency of planet formation in general.

  • Terrestrial planet formation in low-mass disks: dependence with initial conditions

  • M. P. Ronco, G. C. de Elía, O. M. Guilera
  • Published online by Cambridge University Press:
    05 January 2015, pp. 218-219
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  • In general, most of the studies of terrestrial-type planet formation typically use ad hoc initial conditions. In this work we improved the initial conditions described in Ronco & de Elía (2014) starting with a semi-analytical model wich simulates the evolution of the protoplanetary disk during the gas phase. The results of the semi-analytical model are then used as initial conditions for the N-body simulations. We show that the planetary systems considered are not sensitive to the particular initial distribution of embryos and planetesimals and thus, the results are globally similar to those found in the previous work.

  • Influence of the inclination damping on the formation of planetary systems

  • Sotiris Sotiriadis, Anne-Sophie Libert, Kleomenis Tsiganis
  • Published online by Cambridge University Press:
    05 January 2015, pp. 220-222
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  • Highly non-coplanar extrasolar systems (e.g. Upsilon Andromedae) and unexpected spin-orbit misalignment of some exoplanets have been discovered. In Libert and Tsiganis (2011), a significant increase of the mutual inclination of some multi-planet systems has been observed during the type II migration, as a result of planet-planet scattering and/or resonant interactions between the planets. Here we investigate the effect of the inclination damping due to planet-disk interactions on the previous results, for a variety of planetary systems with different initial configurations and mass ratios. Using the damping formulae for eccentricity and inclination provided by the numerical hydrodynamical simulations of Bitsch et al. (2013), we examine their impact on the possible multiple resonances between the planets and how the growth in eccentricity and inclination is affected.

  • Rapid clump formation in discs of young stellar objects class O-I

  • Olga P. Stoyanovskaya, Valeriy N. Snytnikov
  • Published online by Cambridge University Press:
    05 January 2015, pp. 223-224
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  • The formation of planetesimals and large bodies in circumstellar discs can be referred to the stage of massive unstable disc emerging due to the gravitational collapse in the molecular cloud. We have simulated the dynamics of gas and boulder clumps in such systems. The features of instability development in massive disc is discussed. Unlike medium-massive discs the massive disc can provide conditions for simultaneous formation of several clumps as a result of overdensity ring fragmentation. We found regimes where 3, 2 or 1 overdensity ring appear in the disc and then fragment into clumps collecting about a half of the disc mass.

  • Can we expect the massive discs around young stellar objects class O-I to be a birthplace of planetesimal?

  • Valeriy N. Snytnikov, Olga P. Stoyanovskaya, Olga A. Stadnichenko
  • Published online by Cambridge University Press:
    05 January 2015, pp. 225-226
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  • Possibility of large bodies formation in massive discs of young stellar objects (YSO) class O-I was investigated. On the stage of YSO O-I the whole of factors: chemical composition of gas and solids, chemical catalytic reactions, the disc self-gravitation, the increased ratio of solids to gas surface density, adiabatic gas cooling provides favorable conditions for gravitational instabilities development. We simulated 3D dynamics of gas and dust under self-consistent gravitational field and reproduced the formation and evolution of the disc around the protostar. We found that for stars of Solar mass there are regimes when the disc of variable mass is unstable for the development of fast gravitational instabilities.

Front Cover and matter

  • IAU volume 9 issue S310 Cover and Front matter

  • Published online by Cambridge University Press:
    05 January 2015, pp. f1-f15
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Back Cover and matter

  • IAU volume 9 issue S310 Cover and Back matter

  • Published online by Cambridge University Press:
    05 January 2015, pp. b1-b3
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Page 4 of 4