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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: 8/21/2023 11:07:43 AM

Paper abstract: We present JWST images of the well-known planetary nebula NGC 6720 (the RingNebula), covering wavelengths from 1.6\mum to 25 \mum. The bright shell isstrongly fragmented with some 20 000 dense globules, bright in H_2, with acharacteristic diameter of 0.2 arcsec and density n_{\rm H} ~ 10^5-10^6cm^{-3}. The shell contains a thin ring of polycyclic aromatic hydrocarbon(PAH) emission. H_2 is found throughout the shell and in the halo. H_2 inthe halo may be located on the swept-up walls of a biconal polar flow. Thecentral cavity is shown to be filled with high ionization gas and shows twolinear structures. The central star is located 2 arcsec from the emissioncentroid of the cavity and shell. Linear features (`spikes') extend outwardfrom the ring, pointing away from the central star. Hydrodynamical simulationsare shown which reproduce the clumping and possibly the spikes. Around tenlow-contrast, regularly spaced concentric arc-like features are present; theysuggest orbital modulation by a low-mass companion with a period of about 280yr. A previously known much wider companion is located at a projectedseparation of about 15 000 au; we show that it is an M2-M4 dwarf. The system istherefore a triple star. These features, including the multiplicity, aresimilar to those seen in the Southern Ring Nebula (NGC 3132) and may be acommon aspect of such nebulae.