  Accurate stellar properties are crucial for determining exoplanet
characteristics. Gaia DR2 presents revised distances, luminosities, and radii
for 1.6 billion stars. Here, we report the calculation of revised radii and
densities for 320 exoplanets using this data and present updated calculations
of the incident flux received by 690 known exoplanets. This allows the
likelihood that those planets orbit in the habitable zone of their host stars
to be reassessed. As a result of this analysis, three planets can be added to
the catalogue of potentially habitable worlds: HIP~67537~b, HD~148156~b, and
HD~106720~b. In addition, the changed parameterisation of BD~+49~898 means that
its planet, BD~+49~898~b, now receives an incident flux that places it outside
the optimistic habitable zone region, as defined by
\citep{Kopparapu2013,Kopparapu2014}. We find that use of the new \textit{Gaia}
data results in a mean increase in calculated exoplanet radius of 3.76\%.
Previously, CoRoT-3 b had been reported as having the highest density of all
known exoplanets. Here, we use updated information to revise the calculated
density of CoRoT-3~b from 26.4$g\:cm^{-3}$ to 17.3$\pm2.9g\:cm^{-3}$. We also
report the densest exoplanet in our dataset, KELT-1~b, with a density of
23.7$\pm4.0g\:cm^{-3}$. Overall, our results highlight the importance of
ensuring the the parameterisation of known exoplanets be revisited whenever
significant improvements are made to the precision of the stellar parameters
upon which they are based.
