English: Artist's impression of how Type Ia supernovae may look like as revealed by spectro-polarimetry observations. The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth. Using observations of 17 supernovae made over more than 10 years with ESO's Very Large Telescope and the McDonald Observatory's Otto Struve Telescope, astronomers inferred the shape and structure of the debris cloud thrown out from Type Ia supernovae. Such supernovae are thought to be the result of the explosion of a small and dense star — a white dwarf — inside a binary system. As its companion continuously spills matter onto the white dwarf, the white dwarf reaches a critical mass, leading to a fatal instability and the supernova. But what sparks the initial explosion, and how the blast travels through the star have long been thorny issues. The study shows that the outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth.