  The prevailing assumption is that all exoplanets are made of ordinary matter.
However, we propose an unconventional possibility that some exoplanets could be
made of dark matter, which we name "dark exoplanets." In this paper, we explore
methods to search for dark exoplanets, including the mass-radius relation,
spectroscopy, missing transit, and transit light curve. Specifically, we focus
on the transit light curve method and demonstrate how to distinguish partially
transparent dark exoplanets from fully opaque ordinary exoplanets using both
observed exoplanet data and dark exoplanet mock data. Our analysis shows that
dark exoplanets with a large radius (above around 10% of the star radius) and a
small optical depth (below around one) can be identified with current telescope
sensitivities.
