The mid-infrared (mid-IR) wavelength regime offers several advantages for following the late-time evolution of supernovae (SNe). First, the peaks of the SN spectral energy distributions shift toward longer wavelengths following the photospheric phase. Second, mid-IR observations suffer less from effects of interstellar extinction. Third, and perhaps most important, the mid-IR traces dust formation and circumstellar interaction at late-times (>100 days) after the radioactive ejecta component fades. The Spitzer Space Telescope has provided substantial mid-IR observations of SNe since its launch in 2003. More than 200 SNe have been targeted, but there are even more SNe that have been observed serendipitously. Here we present the results of a comprehensive study based on archival Spitzer/IRAC images of more than 1100 SN positions; from this sample, 119 SNe of various subclasses have been detected,

Supernova (SN) explosions have been sought for decades as a possible source of dust in the Universe, providing the seeds of galaxies, stars, and planetary systems. SN 1987A offers one of the most promising examples of significant SN dust formation, but until the James Webb Space Telescope (JWST), instruments have traditionally lacked the sensitivity at both late times (>1 yr post-explosion) and longer wavelengths (i.e. >10 μm) to detect analogous dust reservoirs. Here we present JWST/MIRI observations of two historic Type IIP SNe, 2004et and SN 2017eaw, at nearly 18 and 5 yr post-explosion, respectively. We fit the spectral energy distributions as functions of dust mass and temperature, from which we are able to constrain the dust geometry, origin, and heating mechanism. We place a 90 per cent confidence lower limit on the dust masses for SNe 2004et and 2017eaw of >0.014 and >4 × 10−4 M⊙, respectively. More dust may exist at even colder temperatures or may be obscured by high optical depths. We conclude dust formation in the ejecta to be the most plausible and consistent scenario. The observed dust is radiatively heated to ∼100–150 K by ongoing shock interaction with the circumstellar medium. Regardless of the best fit or heating mechanism adopted, the inferred dust mass for SN 2004et is the second highest (next to SN 1987A) mid-infrared inferred dust mass in extragalactic SNe thus far, promoting the prospect of SNe as potential significant sources of dust in the Universe.

We present an extensive analysis of the late-time mid-infrared (mid-IR) evolution of the Type IIb SN 1993J from 10–26 yr post-explosion based on archival – mostly previously unpublished – photometric data from the Spitzer Space Telescope in conjunction with an archival InfraRed Spectrograph spectrum. SN 1993J is one of the best-studied supernovae (SNe) with an extensive decade-long multiwavelength data set published in various papers; however, its detailed late-time mid-IR analysis is still missing from the literature. Mid-IR data follow not just the continuously cooling SN ejecta but also late-time dust-formation and circumstellar-interaction processes. We provide evidence that the observed late-time mid-IR excess of SN 1993J can be described by the presence of two-component local dust with a dust mass of ∼(3.5–6.0) × 10−3 M⊙ in the case of a partly silicate-based dust composition. The source of these components could be either newly formed dust grains or heating of pre-existing dust via ongoing circumstellar matter interaction also detected at other wavelengths. If it is newly formed, the dust is assumed to be located both in the unshocked inner ejecta and in the outer cold dense shell, just as in the Cassiopeia A remnant and also assumed in other dust-forming SNe a few years after explosion.