A new attempt to solve the type Ia supernova problem

Supernovae distribute most of the chemical elements that we are made of and are detected daily, yet we still do not know how they explode. Type Ia supernovae consist of most recorded supernovae and are likely the result of thermonuclear explosions of white dwarfs (common compact stars with mass similar to the sun and radius similar to earth), but what mechanism causes about 1% of white dwarfs to ignite remains unknown. I will describe our ongoing recent attempt to solve this puzzle that involves a new potential answer - direct collisions of white dwarfs in multiple stellar systems, new robust tools to compare explosion models to observations - in particular the use of global conservation of energy in emitted radiation,  and new key observations  - in particular late-time spectra of ~100 recent supernovae.