JWST observations of the Ring Nebula (NGC 6720): III. A dusty disk around its Central Star

The planetary nebula NGC 6720, also known as the “Ring Nebula”, is one of the most iconic examples 27 of nearby planetary nebulae whose morphologies present a challenge to our theoretical understanding 28 of the processes that govern the deaths of most stars in the Universe that evolve on a Hubble time. 29 We present new imaging with JWST of the central star of this planetary nebula (CSPN) and its close 30 vicinity, in the near- to mid-IR wavelength range. We find the presence of a dust cloud around the CSPN, both from the spectral energy distribution at wavelengths > 31 ∼5 µm, as well as radially-extended 32 emission in the 7.7, 10 and 11.3 µm images. From modeling of these data, we infer that the CSPN 33 has a luminosity of 310L⊙, and is surrounded by a dust cloud with a size of ∼2600 au, consisting of relatively small amorphous silicate dust grains (radius ∼0.01 µm) with a total mass of 1.9 × 10 34 −6 M⊕. 35 However, our best-fit model shows a significant lack of extended emission at 7.7 µm – we show that such emission can arise from a smaller (7.3 × 10 36 −7 M⊕) but uncertain mass of (stochastically-heated) 37 ionized PAHs. However, the same energetic radiation also rapidly destroys PAH molecules, suggesting 38 that these are most likely being continuously replenished, via the outgassing of cometary bodies and/or 39 the collisional grinding of planetesimals. We also find significant photometric variability of the central 40 source that could be due to the presence of a close dwarf companion of mass ≤0.1 M⊙.