  The presence of Jupiter is crucial to the architecture of the Solar System
and models underline this to be a generic feature of planetary systems. We find
the detection of the difference between the position and motion recorded by the
contemporary astrometric satellite Gaia and its precursor Hipparcos can be used
to discover Jupiter-like planets. We illustrate how observations of the nearby
star $\varepsilon$ Indi A giving astrometric and radial velocity data can be
used to independently find the orbit of its suspected companion. The radial
velocity and astrometric data provide complementary detections which allow for
a much stronger solution than either technique would provide individually. We
quantify $\varepsilon$ Indi A b as the closest Jupiter-like exoplanet with a
mass of 3 $M_{Jup}$ on a slightly eccentric orbit with an orbital period of 45
yr. While other long-period exoplanets have been discovered, $\varepsilon$ Indi
A b provides a well constrained mass and along with the well-studied brown
dwarf binary in orbit around $\varepsilon$ Indi A means that the system
provides a benchmark case for our understanding of the formation of gas giant
planets and brown dwarfs.
