Recent observations with the ESO Very Large Telescope have placed strong constraints on the origin and evolution of magnetic fields in white dwarfs, as well as on their interaction with the remnants of surrounding planetary systems. After reviewing work carried out since the discovery of the first magnetic white dwarf, I will present the main results obtained over the past five years. These can be summarised as follows.

1. There are at least two distinct formation channels for magnetic fields in white dwarfs: one associated with ultra-massive white dwarfs formed through the merger of two white dwarfs, and another linked to white dwarfs produced by single-star evolution.

2. Magnetic fields can regulate the accretion of material from planetary debris and are likely responsible for the formation and long-term stability of metal-rich patches at the magnetic poles of polluted white dwarfs.

3. In old white dwarfs, strong magnetic fields are symmetric about the stellar rotation axis. This symmetry may result from magnetic field evolution, or it may be an intrinsic feature of a field-generation process generally occurring after the onset of core crystallisation.

recording: www.youtube.com/watch