A story of singular degeneracy

摘要

Astronomers have a choice of two models of how type la supemovae arise. The progenitor for one of these huge stellar explosions has now been discovered, bringing a definitive judgement a little closer. On page 802 of this issue, Voss and Nelemans1 report that they have found a luminous source of low-energy X-rays at just the position where, on 5 November last year, the type la supernova SN2007on was sighted. The discovery, made in archive data from NASA's Chandra X-ray-observatory satellite, is the first-ever detection of the progenitor of a supernova of this class. It lends support to one particular model for their origin: the 'single degenerate' model, in which the transfer of mass from a normal hydrogen-burning star to an exhausted white-dwarf star triggers the white dwarf to explode.