New origin for supernovae detected

Los Angeles Times : For the first time, a nova-producing systemâmdash;a white dwarf orbiting a red giantâmdash;has been determined to be the source of a Type Ia supernova. Novae are produced when a white dwarf slowly accretes enough hydrogen from a neighboring star to ignite a hydrogen fusion explosion. A Type Ia supernova follows a similar process, except it accumulates material much more quickly, resulting in an explosion in which the fusion of heavier elements occurs. Type Ia supernovae have been used as “standard candles” for determining interstellar distances because they are considered to be created by identical processes and therefore have the same intrinsic brightness. Because the rate of material accretion is so different between nova-producing and supernova-producing systems, it was not considered possible for a supernova to originate from a nova-producing system. However, recently observed supernova PTF 11kx, which was produced by a white dwarfâred giant binary system, suggests otherwise. A team of astronomers led by Ben Dilday of the University of California, Santa Barbara, has found that the supernova resides in a cloud of debris produced by earlier novae from the same system.