Type Ia Supernova Explosions with COSI

Type Ia supernovae (SN), which result from thermonuclear explosions of white dwarf stars, are vital astrophysical tools. They are key standard candles for measuring cosmic distances and play a significant role in enriching galaxies with iron-group elements. However, their progenitor systems and explosion mechanisms remain uncertain, which likely contribute to systematic errors in cosmological measurements. Gamma-ray observations measure nuclear lines, providing unique insight into nucleosynthetic yields and the innermost ejecta, directly detecting the radioactive decay of ⁵⁶Ni → ⁵⁶Co → ⁵⁶Fe that powers the optical light curve. Gamma-ray observations of SN 2014J mark the first - and so far only - gamma-ray detection from a Type Ia SN. This provided the first direct confirmation of radioactive decay in a Type Ia SN. The upcoming Compton Spectrometer and Imager (COSI), scheduled for launch in 2027, will provide multiple gamma-ray detections of Type Ia SN. We will discuss the expected detection rates with COSI out to 20 Mpc and discuss what can be learned by studying these events through gamma-rays.