Abstract: There is evidence that most stars have circumstellar material that originates from the asteroids and comets of their planetary systems. What are the compositions of these small rocky objects around other stars? One way to answer this question is to use the ~30% of white dwarf stars that have unexpected heavy elements polluting their photospheres. This pollution of the normally pristine white dwarf sometimes arises from the accretion of small planetary system objects (planetesimals) that end up within the white dwarf’s tidal radius or Roche limit. These planetesimals sublimate---forming a gas disk---and accrete onto the white dwarf surface, revealing themselves through emission and absorption features from constituent elements. In this talk, I give a broad overview of polluted white dwarfs and describe what we have learned from them thus far. I also highlight my database of models created with the radiative transfer code, CLOUDY, for these types of systems. These models provide a key to quickly understand the instantaneous composition and other properties of the material flowing from these (exo)planetesimals, and will eventually make this type of modeling more accessible in the future.