  White dwarfs have atmospheres that are expected to consist nearly entirely of
hydrogen and helium, since heavier elements will sink out of sight on short
timescales. However, observations have revealed atmospheric pollution by
heavier elements in about a quarter to a half of all white dwarfs. While most
of the pollution can be accounted for with asteroidal or dwarf planetary
material, recent observations indicate that larger planetary bodies, as well as
icy and volatile material from Kuiper belt analog objects, are also viable
sources of pollution. The commonly accepted pollution mechanisms, namely
scattering interactions between planetary bodies orbiting the white dwarfs, can
hardly account for pollution by objects with large masses or long-period
orbits. Here we report on a mechanism that naturally leads to the emergence of
massive body and icy and volatile material pollution. This mechanism occurs in
wide binary stellar systems, where the mass loss of the planets' host stars
during post main sequence stellar evolution can trigger the Eccentric
Kozai-Lidov mechanism. This mechanism leads to large eccentricity excitations,
which can bring massive and long-period objects close enough to the white
dwarfs to be accreted. We find that this mechanism readily explains and is
consistent with observations.
