A New Era for Supernova Science with the James Webb Space Telescope

The gist: The James Webb Space Telescope provides a new window into supernova physics, progenitors, dust production, redshift evolving stellar populations, and cosmology since its launch.

Nearby Supernova Breakthroughs

JWST observations have provided detailed views of nearby SNe in the rest-frame IR and the first spectroscopic samples of high-z SNe in the rest-frame UV-optical. Dust is a key agent shaping the observable universe, as SNe are among the few environments capable of producing dust under extreme conditions. Understanding when and how dust forms in SNe provides a window into the origins of cosmic dust seen at high redshift. Pre-JWST observations revealed that dust formation can occur over a wide range of timescales, from a few hundred days to several years after explosion. Early dust formation is often detected in the dense, cooling gas behind shocks driven by ejecta, circumstellar interaction, or years later as the ejecta cools. JWST/MIRI has been capable of probing new dust formation at early times and uncovering colder dust reservoirs at later times due to its sensitivity out to 25 µm. Recent JWST observations have provided the first detailed mid-infrared spectra of both early and late phases, enabling direct constraints on dust composition, temperature, and spatial distribution. These nearby SNe span a range of subclasses, and assuming the dust origin and heating mechanism can be constrained, these objects provide rare opportunities to directly measure the total dust yield from core-collapse SNe once the ejecta have cooled and expanded sufficiently for mid-infrared emission to emerge unobscured. JWST/MIRI medium resolution spectroscopy (MRS) of these systems can further characterize the dust composition (silicate or carbonaceous), geometry, and optical depth. These studies suggest that SNe can produce substantial dust masses that survive, potentially accounting for the large dust reservoirs observed in the early universe.

Progenitors of Type Ia Supernovae

Nebular-phase observations in the near- and mid-infrared hold immense promise for answering several outstanding questions regarding SNe Ia, including the nature of the circumstellar material in the progenitor system. Early JWST observations have primarily focused on obtaining nebular-phase spectra for the diversity of SNe Ia subtypes. The normal-bright SN 2021aefx showed broad stable [Ni] features, indicative of high-density burning in a massive (M > 1.2M⊙) white dwarf. Observations of SNe 2024pxl and 2024vjm, both members of the Iax subclass, taken ∼ 10−45 days after maximum light simultaneously show P Cygni and nebular lines, and are well matched by spectral models of weak deflagrations. Panchromatic observations of the 03fg-like SN 2022pul reveal a strong thermal dust continuum beyond 2.5 µm, with the presence of [O I] and [Ne II] emission and large scale asymmetries in some line profiles supporting origins from a violent merger within C/O-rich circumstellar medium (CSM).

Supernovae used for Cosmology

Strongly lensed SNe are a purely geometrical probe of H0 which is fully independent from local distance ladder and early-Universe measurements because the time delays depend on the lens total mass distribution and on the time-delay distance, which is inversely proportional to the Hubble constant (H0). JWST has revolutionized this field with its discovery of six more cluster-scale lensed SNe in the last ∼two years, including two that provided new H0 measurements: SN H0pe (H0 = 75.7 +8.1-5.5 km s−1 Mpc−1) and SN Encore (H0 = 66.9 +11.2-8.1 km s−1 Mpc−1). These discoveries have tripled the cosmology sample in a very short time-frame. Testing for Type Ia Supernova Evolution involves checking if SNe Ia standardization at high-z is consistent with low-z, as anomalous distance measurements could indicate evolving dark energy and/or redshift-dependent SN Ia luminosity biases. JWST has provided several of the first spectroscopically confirmed SNe Ia at z ≳ 2, enabling an initial glimpse into the presence of any redshift-dependent luminosity biases. The existing sample suggests no extreme evolution in SNe Ia that could be significantly biasing existing cosmological measurements, though a larger sample at z > 2 will be needed to limit such systematics to below the level required for the Nancy Grace Roman Space Telescope.

New Insights into the Core-Collapse Supernova Population

Building large samples of SNe for population inferences is important because environmental conditions of distant (z ≳ 2) Universe differ drastically from local Universe conditions, making it plausible that general properties of SN progenitors are significantly different at high-z. The JADES Transient Survey discovered 79 SNe out to z = 4.82, with nearly half of the sample (38 SNe) at z > 2. A subset of these included a broad-line Type Ic SN at z = 2.83 and an SN IIP at z = 3.61. The rapid discovery of a high-z SN Ic broadline in a relatively small survey area may imply that SNe Ic-BL are more common at high-z. The JWST program is expected to discover ∼90 SNe (∼45 at z > 2) and spectroscopically classify ∼30 SNe, providing the first definitive measurement of CC SN rates at z > 2.

Zooming in on a Core-Collapse Supernova at z = 5.13

High S/N (≳ 10) spectroscopy has only been possible at z < 3 thus far, and only for a handful of objects. The large magnifications afforded by galaxy cluster lensing systems can greatly increase the signal of very distant sources, providing rare opportunities to study extremely distant SNe in extraordinary detail. SN Eos, a doubly-imaged, strongly lensed transient at z = 5.13 is the highest-redshift (z = 5.13) SN yet spectroscopically classified. Analysis of the spectrum and light curve of SN Eos revealed that it is of the type IIP sub-class, originating from a collapse of a massive star with Z ≲ 0.1Z⊙.

Summary and Discussion

JWST has provided insights into dust production in CC SNe, which could account for large dust reservoirs in the early universe, as well as some of the first mid-IR nebular phase spectroscopy for SNe Ia. At higher redshifts, JWST has made contributions to cosmology at large with two new measurements of H0 using strongly lensed SNe and constraints on redshift-dependent SN Ia luminosity biases that could strongly impact future dark energy measurements. JWST has provided new constraints on CC SNe through surveys building large samples for population level inferences and novel rate measurements, as well as detailed views (with the aid of gravitational lensing) of the most distant CC SN yet observed. The Roman Space Telescope is expected to launch in mid-2026 and will execute the HLTDS, which will be an excellent source of cosmologically useful lensed SNe, high-z SNe, and rest-frame near-IR observations of low-z SNe. JWST will continue to play a key complementary role into the future as it continues to build unique datasets for a diverse sample of SNe.

How it works

1. Dust production in CC SNe is traced by observing warm dust emission and molecular precursors like CO and SiO, which act as key cooling agents allowing ejecta to reach temperatures where dust can condense. JWST/MIRI's sensitivity out to 25 µm is much more capable of probing new dust formation at early times and uncovering colder dust reservoirs at later times.

2. Progenitor studies for SNe Ia leverage nebular-phase spectra to investigate the nature of circumstellar material, whether SNe Ia can form molecules or dust, and how flux redistributes in the ejecta with time. JWST observations have focused on obtaining nebular-phase spectra for the diversity of SN Ia subtypes.

3. Cosmological constraints from strongly lensed SNe rely on time delays which depend on the lens total mass distribution and the time-delay distance, which is inversely proportional to H0. These measurements are independent from local distance ladder and early-Universe measurements.

1. A new JWST-powered automated dust formation model can be developed by incorporating detailed views of nearby SNe in the rest-frame IR to detailed constraints on dust composition, temperature, and spatial distribution, allowing AI to predict when and how dust forms across different explosion types.

2. An AI system can be trained to perform nebular-phase spectroscopy analysis for Type Ia Supernovae by using JWST/MIRI MRS data, enabling the determination of the nature of the circumstellar material in the progenitor system and whether SNe Ia can form molecules or dust.

3. A cosmological inference engine can be improved to incorporate gravitationally lensed SNe by using photometry that does not include reference imaging to produce new H0 measurements, as these objects provide a way to probe cosmology fully independent from local distance ladder and early-Universe measurements.

4. A high-redshift population modeling tool can be enhanced to constrain the initial mass function (IMF) and massive-star-population changes by analyzing the general properties of SN progenitors (and SNe themselves) at high-z compared to low-z conditions.

5. A search algorithm for faint, distant transients can be optimized using JWST's sensitivity to discover high-redshift SNe, specifically targeting the detection of extremely distant SNe in the rest-frame ultraviolet (UV)-optical.