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Water vapour and hydrogen in the terrestrial-planet-forming region of a protoplanetary disk


Planetary systems (ours included) formed in disks of dust and gas around young stars. Disks are an integral part of the star and planet formation process1,2, and knowledge of the distribution and temperature of inner-disk material is crucial for understanding terrestrial planet formation3, giant planet migration4, and accretion onto the central star5. Although the inner regions of protoplanetary disks in nearby star-forming regions subtend only a few nano-radians, near-infrared interferometry has recently enabled the spatial resolution of these terrestrial zones. Most observations have probed only dust6, which typically dominates the near-infrared emission. Here I report spectrally dispersed near-infrared interferometric observations that probe the gas (which dominates the mass and dynamics of the inner disk), in addition to the dust, within one astronomical unit (1 au, the Sun–Earth distance) of the young star MWC 480. I resolve gas, including water vapour and atomic hydrogen, interior to the edge of the dust disk; this contrasts with results of previous spectrally dispersed interferometry observations7,8. Interactions of this accreting gas with migrating planets may lead to short-period exoplanets like those detected around main-sequence stars4. The observed water vapour is probably produced by the sublimation of migrating icy bodies9, and provides a potential reservoir of water for terrestrial planets10.

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Figure 1: Angular size of the near-infrared emission from MWC 480 as a function of wavelength.
Figure 2: Measured V 2 and fluxes, compared to the predictions of simple physical models.
Figure 3: The environment within 1  au of the young star MWC 480.


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Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency’s scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. I thank the entire Keck Interferometer team for their invaluable contributions to these observations. I also acknowledge input into this work (and this manuscript) from R. Akeson, E. Chiang, A. Glassgold, J. Graham, J. Najita and R. White. I am supported by a Miller Research Fellowship.

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Correspondence to J. A. Eisner.

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Supplementary information

Supplementary Information

This file contains Supplementary Notes with additional evidence that effects in the data attributed to water vapor emission are not artifacts of the data calibration or modeling procedures and Supplementary Figure 1 with Legend. (PDF 110 kb)

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Eisner, J. Water vapour and hydrogen in the terrestrial-planet-forming region of a protoplanetary disk. Nature 447, 562–564 (2007).

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