Spectropolarimetric diagnostics of thermonuclear supernova

Even at extragalactic distances, the shape of Supernova (SN) ejecta can be effectively diagnosed by spectropolarimetry. We present here results for 12 Type Ia supernovae (SNe) obtained during the past years through our program of SN polarimetry, using primarily the Very Large Telescopes (VLT) of European Southern Observatory (ESO). These observations show that SN Ia ejecta typically consist of a smooth, central iron rich core and an outer layer with significant asymmetries and chemical inhomogeneities. The degree of this peripheral asphericity is anti-correlated with the intrinsic luminosity of Type Ia supernovae.