skade88 writes "Wired has a good article that covers the origins of the white dwarf super nova Johannes Kepler observed in 1604. From the article: 'Up until now, it was unclear what lead to the star's explosion. New Chandra data suggests that, at least in the case of Kepler's remnant, the white dwarf grabbed material from its companion star. The disk-shaped structure seen near the center suggests that the supernova explosion hit a ring of gas and dust that would have formed, like water circling a drain, as the white dwarf sucked material away from its neighbor. In addition, magnesium is not an element formed in great abundances during Type 1a supernovas, suggesting it came from the companion star. Whether or not Kepler's supernova is a typical case remains to be seen. '"