Future stellar flybys of the Voyager and Pioneer spacecraft
  The Pioneer 10 and 11 and Voyager 1 and 2 spacecraft, launched in the 1970s,
are heading out of the solar system. Using the astrometric and radial velocity
data from the second Gaia data release, we integrate the trajectories of 7.4
million stars, and the spacecraft, through a Galactic potential in order to
identify those stars the spacecraft will pass closest to. The closest
encounters for all spacecraft take place at separations between 0.2 and 0.5 pc
within the next million years. The closest encounter will be by Pioneer 10 with
the K8 dwarf HIP 117795, at 0.23 pc in 90 kyr at a high relative velocity of
291 km/s.
