CO in the Helix nebula

The detection of CO (2-1) emission from the Helix planetary nebula is reported. The spatial distribution and kinematics of the CO emission indicate that the molecular gas is closely associated with the prominent ring structures seen in optical photographs. The CO velocity varies systematically with position in the nebula and is consistent with the simple kinematics of two expanding toroids. Mass estimates indicate that at least one-tenth of the nebular material has not yet been ionized by the central star. 10 references