White dwarfs become magnetic as they get older

At least one out of four white dwarfs (WDs) will end its life as a magnetic star, and therefore magnetic fields are an essential component of WD physics. New insights into the magnetism of degenerate stars from a recent analysis of a volume-limited sample of WDs have provided the best evidence obtained so far of how the frequency of magnetism in WDs correlates with age. This could help to explain the origin and evolution of magnetic fields in WDs.