JWST Discovery of Dust Reservoirs in Nearby Type IIP Supernovae 2004et\n and 2017eaw

Supernova (SN) explosions have been sought for decades as a possible source\nof dust in the Universe, providing the seeds of galaxies, stars, and planetary\nsystems. SN 1987A offers one of the most promising examples of significant SN\ndust formation, but until the James Webb Space Telescope (JWST), instruments\nhave traditionally lacked the sensitivity at both late times (>1 yr\npost-explosion) and longer wavelengths (i.e., >10 um) to detect analogous dust\nreservoirs. Here we present JWST/MIRI observations of two historic Type IIP\nSNe, 2004et and SN 2017eaw, at nearly 18 and 5 yr post-explosion, respectively.\nWe fit the spectral energy distributions as functions of dust mass and\ntemperature, from which we are able to constrain the dust geometry, origin, and\nheating mechanism. We place a 90% confidence lower limit on the dust masses for\nSNe 2004et and 2017eaw of >0.014 and >4e-4 M_sun, respectively. More dust may\nexist at even colder temperatures or may be obscured by high optical depths. We\nconclude dust formation in the ejecta to be the most plausible and consistent\nscenario. The observed dust is radiatively heated to ~100-150 K by ongoing\nshock interaction with the circumstellar medium. Regardless of the best fit or\nheating mechanism adopted, the inferred dust mass for SN 2004et is the second\nhighest (next to SN 1987A) inferred dust mass in extragalactic SNe thus far,\npromoting the prospect of SNe as potential significant sources of dust in the\nUniverse.\n