HST/NICMOS Imaging of the Planetary Nebula Hubble 12
Joseph L. Hora, William B. Latter, Aditya Dayal, John Bieging, Douglas M. Kelly, A. G. G. M. Tielens, Susan R. Trammell
Abstract
Images of Hubble 12 were obtained with the HST/NICMOS instrument in the F110W, F164N, and F166N filters of NIC1, and the F160W, F187N, F190N, F212N, F215N filters of NIC2. The images show the structure of the inner ``torus'' and lobes much clearer than previous ground-based images. In particular, the [Fe II] lobes are clearly resolved and shown to be distinct from the molecular hydrogen emission structures. Apparent changes in the inner ionized and neutral bipolar shell implies periodic mass loss or changes in stellar wind shape or direction. The molecular hydrogen in the ``eye'' is radiatively excited and shows a complex morphology that suggests that several mass ejection events are responsible for producing this structure. The position angle of the molecular hydrogen and [Fe II] lobes differ, indicating a possible precession of the ejection axis.
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