The edge-on disk surrounding the nearby young star  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  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 rotation^{1, 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  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.

1. Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
2. Department of Physics & Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
3. Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington DC 20015, USA
4. Laboratoire d'Astrophysique de Marseille, BP 8, F-13376 Marseille cedex 12, France

Correspondence to: Aki Roberge¹ Correspondence and requests for materials should be addressed to A.R. (Email: akir@milkyway.gsfc.nasa.gov).

Received 23 January 2006 | Accepted 24 April 2006

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