  Infrared excesses due to dusty disks have been observed orbiting white dwarfs
with effective temperatures between 7200 K and 25000 K, suggesting that the
rate of tidal disruption of minor bodies massive enough to create a coherent
disk declines sharply beyond 1~Gyr after white dwarf formation. We report the
discovery that the candidate white dwarf LSPM J0207+3331, via the Backyard
Worlds: Planet 9 citizen science project and Keck Observatory follow-up
spectroscopy, is hydrogen-dominated with a luminous compact disk (L$_{\rm
IR}$/L$_{\star}$=14%) and an effective temperature nearly 1000K cooler than any
known white dwarf with an infrared excess. The discovery of this object places
the latest time for large scale tidal disruption events to occur at $\sim$3 Gyr
past the formation of the host white dwarf, making new demands of dynamical
models for planetesimal perturbation and disruption around post main sequence
planetary systems. Curiously, the mid-IR photometry of the disk cannot be fully
explained by a geometrically thin, optically thick dust disk as seen for other
dusty white dwarfs, but requires a second ring of dust near the white dwarf's
Roche radius. In the process of confirming this discovery, we found that
careful measurements of WISE source positions can reveal when infrared excesses
for white dwarfs are co-moving with their hosts, helping distinguish them from
confusion noise.
