  Direct imaging of gas giant exoplanets provides key information on planetary
atmospheres and the architectures of planetary systems. However, few planets
have been detected in blind surveys used to achieve imaging detections. Using
Gaia and Hipparcos astrometry we identified dynamical evidence for a gas giant
planet around the nearby star HIP 99770 and then confirmed this planet by
direct imaging with the Subaru Coronagraphic Extreme Adaptive Optics Project.
HIP 99770 b orbits 17 astronomical units from its host star, with an insolation
comparable to Jupiter's and a dynamical mass of 13.9--16.1 Jupiter masses. Its
planet-to-star mass ratio (7--8$\times$10$^{-3}$) is comparable to that other
directly-imaged planets. The planet's atmosphere resembles an older,
less-cloudy analogue of the atmospheres of previously-imaged exoplanets around
HR 8799.
