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Stabilization of the disk around β Pictoris by extremely carbon-rich gas


The edge-on disk surrounding the nearby young star β Pictoris is the archetype of ‘debris disks’, which are composed of dust and gas produced by collisions between—and evaporation of—planetesimals, analogues of Solar System comets and asteroids. These disks may provide insight into the formation and early evolution of terrestrial planets. Previous work on β Pic concluded that the disk gas has roughly solar abundances of elements1, but this poses a problem because such gas should rapidly be blown away from the star, contrary to observations showing a stable gas disk in keplerian rotation1,2. Here we report the detection of singly and doubly ionized carbon (C ii, C iii) and neutral atomic oxygen (O i) gas in the β Pic disk. Carbon is extremely overabundant relative to every other measured element. This appears to solve the problem of the stable gas disk, because the carbon overabundance should keep the gas disk in keplerian rotation3. The overabundance may indicate that the gas is produced from material more carbon-rich than expected of Solar System analogues.

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Figure 1: Circumstellar absorption lines in far-ultraviolet spectra of β Pic.
Figure 2: Bulk composition of β Pic stable circumstellar gas.

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We thank D. Lindler for recalibrating the archival STIS spectra used in this paper. The work at JHU was supported by NASA.

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Correspondence to Aki Roberge.

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Reprints and permissions information is available at The authors declare no competing financial interests.

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Supplementary Notes

This document contains details of the observations and analysis. It includes one Supplementary Figure showing contours of χ2 from analysis of the OI absorption line. The document has three Supplementary Tables, 1) an observation log, 2) a complete inventory of all species in the β Pic stable gas, and 3) a table with calculated elemental ionization fractions. (PDF 71 kb)

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Roberge, A., Feldman, P., Weinberger, A. et al. Stabilization of the disk around β Pictoris by extremely carbon-rich gas. Nature 441, 724–726 (2006).

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