Exact progenitors and explosion mechanisms of Type Ia supernovae

Determine the exact details of the progenitor scenarios and explosion mechanisms that produce Type Ia supernovae, including specifying the physical conditions and pathways under which single-degenerate, double-degenerate, or higher-multiplicity systems lead to the thermonuclear disruption of carbon–oxygen white dwarfs.

Background

The paper investigates the nebular-phase mid-infrared spectrum of SN 2021aefx with JWST/MIRI and interprets the observations using delayed-detonation models near the Chandrasekhar mass. Despite progress for this particular event, the broader astrophysical question of the exact progenitor channels and explosion mechanisms for Type Ia supernovae remains unsettled across the population.

The authors review leading scenarios (single-degenerate vs. double-degenerate, and multiple-star systems) and explosion mechanisms (near-Chandrasekhar mass delayed detonation vs. sub-Chandrasekhar detonations), emphasizing their complex interplay and the importance of resolving this uncertainty for nucleosynthesis and cosmological applications.

References

Type Ia Supernovae (SNe~Ia) originate from the thermonuclear disruption of a carbon-oxygen (C-O) White Dwarf (WD) in a multiple star system \citep{Hoyle1960}; yet to date, the exact details of their progenitor scenarios or explosion mechanisms are unknown.

— A JWST Medium Resolution MIRI Spectrum and Models of the Type Ia supernova 2021aefx at +415 d  (2404.17043 - Ashall et al., 2024) in Section 1 (Introduction)

Only UV spectroscopy enables the study of white dwarf binaries in detail, and it is needed to answer several key key scientific questions: What mechanisms drive binary evolution? Which pathways produce successful SN Ia explosions? How do different classes of gravitational-wave sources form? How much processed material is returned to the ISM by nova eruptions and SNe Ia? What is the origin of magnetism?

— The future of high-resolution UV spectroscopy: Science with a UV Échelle spectrograph on the Habitable Worlds Observatory, or a dedicated mission  (2609.09329 - Cia et al., 8 Sep 2026) in Section 4, subsection “White dwarfs and compact binaries”

This is challenging: the {\it HST}, NIRCam, and MIRI observations were obtained a few years apart (the most recent NIRCam data only $\sim$4 months before explosion), so describing the combined dataset with a single, time-independent model is not necessarily well justified, if the system is evolving and it is not known how such a system may appear immediately before explosion.

— JWST Detects a Dusty AGB-like Source Before the Type Ia-CSM Supernova 2026sqf  (2608.13321 - Szalai et al., 13 Aug 2026) in Section 2.2, “SED of the potential progenitor system” (Section 2, Data & Analysis)

Binary interaction shortly before the explosion is a natural explanation, though the channel and timescale remain uncertain.

— JWST Detects a Dusty AGB-like Source Before the Type Ia-CSM Supernova 2026sqf  (2608.13321 - Szalai et al., 13 Aug 2026) in Abstract

Despite intensive observational study, the physical origin of the HVF remains unclear. The question of the origin of HVFs is closely tied to our fundamental (and so far unanswered) questions about the progenitors and explosion mechanism(s) of Type Ia SNe as a whole.

— Fast and furious -- High-velocity features of Ca and Si in the spectra of Type Ia supernovae  (2609.37719 - Bora et al., 29 Sep 2026) in Section 1, Introduction; Section 5, Discussion; Section 6, Conclusions