But in this work, the researchers show how a white dwarf's magnetic fields can concentrate the debris, making detection more difficult. "Since both magnetism and debris disks of tidally disrupted bodies are common around white dwarfs, many previous studies have investigated the process of magnetic accretion onto white dwarfs," the authors write. They found that if there's misalignment between the white dwarf's spin poles and magnetic fields, then patchy white dwarfs can have pollution signatures that vary periodically. The magnetic fields could be fossil fields from before it became a white dwarf, they could be from the crystallization of the white dwarf's core, or they could be from binary interactions. Each of these three origins shapes leaves their fingerprints on the white dwarf atmospheres, and understanding white dwarf accretion of planetary systems requires a better understanding of white dwarf atmospheres.