Exoplanets as Sub-GeV Dark Matter Detectors
  We present exoplanets as new targets to discover Dark Matter (DM). Throughout
the Milky Way, DM can scatter, become captured, deposit annihilation energy,
and increase the heat flow within exoplanets. We estimate upcoming infrared
telescope sensitivity to this scenario, finding actionable discovery or
exclusion searches. We find that DM with masses above about an MeV can be
probed with exoplanets, with DM-proton and DM-electron scattering cross
sections down to about $10^{-37}$cm$^2$, stronger than existing limits by up to
six orders of magnitude. Supporting evidence of a DM origin can be identified
through DM-induced exoplanet heating correlated with Galactic position, and
hence DM density. This provides new motivation to measure the temperature of
the billions of brown dwarfs, rogue planets, and gas giants peppered throughout
our Galaxy.
