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JWST observations of the Ring Nebula (NGC 6720): I. Imaging of the rings, globules, and arcs Published: 8/17/2023 6:01:55 PM Updated: 8/17/2023 6:01:55 PM

Paper abstract: We present \textit{JWST} images of the well-known planetary nebula NGC\,6720(the Ring Nebula), covering wavelengths from 1.6\mum to 25 \mum. The brightshell is strongly fragmented with some 20\,000 dense globules, bright in H_2,with a characteristic diameter of 0.2~arcsec and density n_{\rm H} ~10^5--10^6\,cm^{-3}. The shell contains a thin ring of polycyclic aromatichydrocarbon (PAH) emission. H_2 is found throughout the shell and in thehalo. H_2 in the halo may be located on the swept-up walls of a biconal polarflow. The central cavity is shown to be filled with high ionization gas andshows two linear structures. The central star is located 2~arcsec from theemission centroid of the cavity and shell. Linear features (`spikes') extendoutward from the ring, pointing away from the central star. Hydrodynamicalsimulations are shown which reproduce the clumping and possibly the spikes.Around ten low-contrast, regularly spaced concentric arc-like features arepresent; they suggest orbital modulation by a low-mass companion with a periodof about 280~yr A previously known much wider companion is located at aprojected separation of about 15\,000~au; we show that it is an M2--M4 dwarf.The system is therefore a triple star. These features, including themultiplicity, are similar to those seen in the Southern Ring Nebula (NGC\,3132)and may be a common aspect of such nebulae.