  Type Ia supernovae luminosities can be corrected to render them useful as
standard candles able to probe the expansion history of the universe. This
technique was successful applied to discover the present acceleration of the
universe. As the number of SNe Ia observed at high redshift increases and
analysis techniques are perfected, people aim to use this technique to probe
the equation of state of the dark energy. Nevertheless, the nature of SNe Ia
progenitors remains controversial and concerns persist about possible evolution
effects that may be larger and harder to characterize than the more obvious
statistical uncertainties.
