Asymmetric Burning in A Normal Type Ia Supernova

I present observations of the nearby and bright Type Ia supernova (SN Ia) 2020ue extending out to +405 days after maximum light. The early-time spectra and photometry are consistent with a normal, unremarkable SN Ia that would included in cosmological analyses. The nebular-phase spectrum, however, exhibits an asymmetric triple-peaked [CaII] emission-line profile that has no counterpart in the literature. I review plausible explanations for the observed asymmetries, and favor a off-center transition from subsonic to supersonic burning (i.e., the deflagration to detonation transition, or DDT). However, this interpretation is not unique and the dearth of nebular-phase SN Ia models hinders progress in our understanding of these cosmic explosions. I will conclude by outlining our upcoming observational programs designed to extend these types of measurements to the extremes of the SN Ia population.