Flows of gas through a protoplanetary gap

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The formation of gaseous giant planets is thought to occur in the first few million years after stellar birth. Models1 predict that the process produces a deep gap in the dust component (shallower in the gas2, 3, 4). Infrared observations of the disk around the young star HD142527 (at a distance of about 140 parsecs from Earth) found an inner disk about 10 astronomical units (au) in radius5 (1au is the Earth–Sun distance), surrounded by a particularly large gap6 and a disrupted7 outer disk beyond 140au. This disruption is indicative of a perturbing planetary-mass body at about 90au. Radio observations8, 9 indicate that the bulk mass is molecular and lies in the outer disk, whose continuum emission has a horseshoe morphology8. The high stellar accretion rate10 would deplete the inner disk11 in less than one year, and to sustain the observed accretion matter must therefore flow from the outer disk and cross the gap. In dynamical models, the putative protoplanets channel outer-disk material into gap-crossing bridges that feed stellar accretion through the inner disk12. Here we report observations of diffuse CO gas inside the gap, with denser HCO+ gas along gap-crossing filaments. The estimated flow rate of the gas is in the range of 7×10−9 to 2×10−7 solar masses per year, which is sufficient to maintain accretion onto the star at the present rate.

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Corrected online 09 January 2013
An affiliation and a figure citation were corrected.


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  1. Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile

    • Simon Casassus,
    • Gerrit van der Plas,
    • Sebastian Perez M &
    • Vachail Salinas
  2. Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura 763-0355, Santiago, Chile

    • William R. F. Dent &
    • Antonio Hales
  3. European Southern Observatory, Casilla 19001, Vitacura, Santiago, Chile

    • William R. F. Dent,
    • Dimitri Mawet &
    • Julien H. Girard
  4. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22903-2475, USA

    • Ed Fomalont,
    • Antonio Hales &
    • Al Wootten
  5. Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290, Versoix, Switzerland

    • Janis Hagelberg
  6. Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Santiago, Chile

    • Andrés Jordán
  7. UMI-FCA, CNRS/INSU France (UMI 3386), and Departamento de Astronomía, Universidad de Chile, Santiago, Chile

    • Francois Ménard
  8. CNRS/UJF Grenoble 1, UMR 5274, Institut de Planétologie et dAstrophysique de Grenoble (IPAG), F-48041 Grenoble Cedex 9, France

    • Francois Ménard
  9. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA

    • David Wilner
  10. Department of Astronomy, UC Berkeley, 601 Campbell Hall, Berkeley, California 94720, USA

    • A. Meredith Hughes
  11. Departamento de Física y Astronomía, Universidad Valparaiso, Avenida Gran Bretana 1111, Valparaiso, Chile

    • Matthias R. Schreiber &
    • Hector Canovas
  12. University Observatory, Ludwig-Maximillians University, D-81679 Munich, Germany

    • Barbara Ercolano
  13. Center of Mathematical Modeling, University of Chile, Avenida Blanco Encalada 2120 Piso 7, Santiago, Chile

    • Pablo E. Román


General design of ALMA project, data analysis and write-up: S.C. Discussion of infrared observations of gas in cavities: G.v.d.P. Hydrodynamical modelling: S.P.M. ALMA data reduction: A.H. and E.F. Infrared-image processing: D.M., J.H. and J.H.G. Contributions to ALMA Cycle 0 proposal: A.J., F.M., D.W. and A.M.H. Design of ALMA observations: A.W., A.H. and S.C. Authors W.R.F.D. to A.W. contributed equally. All authors discussed the results and commented on the manuscript.

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