A Search for Asteroids, Moons, and Rings Orbiting White Dwarfs
  Do white dwarfs host asteroid systems? Although several lines of argument
suggest that white dwarfs may be orbited by large populations of asteroids,
transits would provide the most direct evidence. We demonstrate that the Kepler
mission has the capability to detect transits of white dwarfs by asteroids.
Because white-dwarf asteroid systems, if they exist, are likely to contain many
asteroids orbiting in a spatially extended distribution, discoveries of
asteroid transits can be made by monitoring only a small number of white
dwarfs, compatible with Kepler's primary mission, which is to monitor stars
with potentially habitable planets. Possible future missions that survey ten
times as many stars with similar sensitivity and minute-cadence monitoring can
establish the characteristics of asteroid systems around white dwarfs, such as
the distribution of asteroid sizes and semimajor axes. Transits by planets
would be more dramatic, but the probability that they will occur is lower.
Ensembles of planetary moons and/or the presence of rings around planets can
also produce transits detectable by Kepler. The presence of moons and rings can
significantly increase the probability that Kepler will discover planets
orbiting white dwarfs, even while monitoring only a small number of them.
