The results are astonishing:
When a star becomes a white dwarf, its planetary system is thrown into chaos. Gravitational perturbations can fling asteroids, comets, and even planetesimals inward. If one of these bodies passes too close to the white dwarf (within its Roche limit), the star's immense tidal forces shred the object into a ring of gas and dust. This ring then spirals into the white dwarf, depositing metals into its atmosphere. white dwarf 109