Direct Detection of Ultralight Dark Matter via Astronomical Ephemeris
  A novel idea of the direct detection to search for a ultralight dark matter
based on the interaction between the dark matter and a nucleon is proposed.
Solar system bodies feel the dark matter wind and it acts as a resistant force
opposing their motions. The astronomical ephemeris of solar system bodies is so
precise that it has a strong capability to detect a dark matter whose mass is
much lighter than O(1) eV. We have estimated the resistant force based on the
calculation of the elastic scattering cross section between the dark matter and
the bodies beyond the Born approximation, and show that the astronomical
ephemeris indeed put a very strong constraint on the interaction between the
dark matter and a nucleon, depending on how smoothly the ultralight dark matter
is distributed at the scale smaller than the celestial bodies in our solar
system.
