Modeling Type Ia supernovae
Type Ia supernovae (SNe Ia) are important tools in observational cosmology, but this is not the only reason why these end stages of the evolution of intermediate-mass stars in binary systems are of fundamental interest. They are the dominant source of iron group elements in the Universe and have a dynamical impact on their surroundings -- and, of course, they are fascinating objects by themselves. Despite their importance, the nature of SNe Ia remains enigmatic. Traditionally, they have been attributed to carbon/oxygen white dwarfs exploding when approaching the Chandrasekhar mass due to accretion from a normal companion star. However, recent observations, as well as theoretical considerations, cast some doubts on this picture as a universal explanation for all objects. Systematic surveys unveil a rich variety within the class of SNe Ia. I will discuss how this can be accounted for in theoretical models. Three-dimensional hydrodynamic explosion simulations are combined with radiative transfer calculations to predict observables that allow direct comparison with astronomical data. Our results suggest that several explosion scenarios may be at work for SNe Ia and that explosions of Chandrasekhar-mass white dwarfs may not be the only explanation for the bulk of them.