Thermonuclear supernova explosions from different progenitor systems

Thermonuclear explosions of white dwarfs are thought to explain Type
Ia supernovae (SNe Ia) -- but it is still unclear how these explosions
come about and how they proceed in detail. This is a fundamental
problem as SNe Ia are key players in many fields of astrophysics
including galactic chemical evolution and observational
cosmology. Since their progenitors elude observation as well as
modeling, I will argue that simulations of explosions arising from
different scenarios can help to overcome the problem. A new generation
of three-dimensional hydrodynamic explosion simulations in combination
with radiative transfer calculations allows us to predict observables
that can be directly compared to astronomical data. Avoiding tunable
parameters in the models, conclusions on progenitor properties are
possible. Contradicting 'textbook wisdom', recent results demonstrated
that a normal SN Ia does not necessarily require the explosion of a
Chandrasekhar-mass white dwarf, but they also do not rule out this
possibility. While the question of the progenitor channel responsible
for the bulk of objects remains open, the synthesis of modeling and
recent observations underpins the emerging picture of SNe Ia being
much less homogeneous than previously thought. This could complicate
their use as cosmic distance indicators.