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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 HD 142527 (at a distance of about 140 parsecs from Earth) found an inner disk about 10 astronomical units (au) in radius5 (1 au is the Earth–Sun distance), surrounded by a particularly large gap6 and a disrupted7 outer disk beyond 140 au. This disruption is indicative of a perturbing planetary-mass body at about 90 au. 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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Figure 1: ALMA observations of HD 142527, with a horseshoe dust continuum surrounding a gap that still contains gas.

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  • 09 January 2013

    An affiliation and a figure citation were corrected.


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This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00465.S. ALMA is a partnership of the ESO, NSF, NINS, NRC, NSC and ASIAA. The Joint ALMA Observatory is operated by the ESO, AUI/NRAO and NAOJ. This work was also based on observations obtained at the Gemini Observatory. Financial support was provided by Millennium Nucleus P10-022-F (Chilean Ministry of Economy) and additionally by grant FONDECYT 1100221 and grant 284405 from the European Union FP7 programme.

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Authors and Affiliations



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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Correspondence to Simon Casassus.

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The authors declare no competing financial interests.

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This file contains Supplementary Text and Data 1-5, Supplementary References and Supplementary Figures 1-13. (PDF 10381 kb)

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Casassus, S., van der Plas, G., M, S. et al. Flows of gas through a protoplanetary gap. Nature 493, 191–194 (2013).

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