Type Ia supernovae ( SNIa ) remain mysterious despite their central importance in cosmology and their rapidly increasing discovery rate .
The progenitors of SNIa can be probed by the delay time between progenitor birth and explosion as SNIa .
The explosions and progenitors of SNIa can be probed by MeV nuclear gamma rays emitted in the decays of radioactive nickel and cobalt into iron .
We compare the cosmic star formation and SNIa rates , finding that their different redshift evolution requires a large fraction of SNIa to have large delay times .
A delay time distribution of the form t ^ { - \alpha } with \alpha = 1.0 \pm 0.3 provides a good fit , implying 50 \% of SNIa explode more than \sim 1 Gyr after progenitor birth .
The extrapolation of the cosmic SNIa rate to z = 0 agrees with the rate we deduce from catalogs of local SNIa .
We investigate prospects for gamma-ray telescopes to exploit the facts that escaping gamma rays directly reveal the power source of SNIa and uniquely provide tomography of the expanding ejecta .
We find large improvements relative to earlier studies by Gehrels et al .
in 1987 and Timmes & Woosley in 1997 due to larger and more certain SNIa rates and advances in gamma-ray detectors .
The proposed Advanced Compton Telescope , with a narrow-line sensitivity \sim 60 times better than that of current satellites , would , on an annual basis , detect up to \sim 100 SNIa ( 3 \sigma ) and provide revolutionary model discrimination for SNIa within 20 Mpc , with gamma-ray light curves measured with \sim 10 \sigma significance daily for \sim 100 days .
Even more modest improvements in detector sensitivity would open a new and invaluable astronomy with frequent SNIa gamma-ray detections .