The dynamics of the giant ring nebula Hubble III in NGC 6822.

The dynamics and the structure of the ring nebula Hubble III in NGC 6822 have been investigated by obtaining absolutely calibrated Hα imagery of the object and Hα line profiles along two orthogonal lines across its face using the Manchester Echelle Spectrometer II. A remarkably symmetric radially expanding bubble is observed with smaller expanding bubbles over its surface. Several possible dynamical origins are examined and models involving stellar wind driven bubbles are found to be the most convincing. The kinematics of the neighbouring nebula Hubble I are also briefly discussed.