Determining reliable distances to classical novae is a challenging but crucial step in deriving their ejected masses and explosion energetics .
Here we combine radio expansion measurements from the Karl G. Jansky Very Large Array with velocities derived from optical spectra to estimate an expansion parallax for nova V959 Mon , the first nova discovered through its \gamma -ray emission .
We spatially resolve the nova at frequencies of 4.5–36.5 GHz in nine different imaging epochs .
The first five epochs cover the expansion of the ejecta from 2012 October to 2013 January , while the final four epochs span 2014 February to 2014 May .
These observations correspond to days 126 through 199 and days 615 through 703 after the first detection of the nova .
The images clearly show a non-spherical ejecta geometry .
Utilizing ejecta velocities derived from 3D modelling of optical spectroscopy , the radio expansion implies a distance between 0.9 \pm 0.2 and 2.2 \pm 0.4 kpc , with a most probable distance of 1.4 \pm 0.4 kpc .
This distance implies a \gamma -ray luminosity much less than the prototype \gamma -ray-detected nova , V407 Cyg , possibly due to the lack of a red giant companion in the V959 Mon system .
V959 Mon also has a much lower \gamma -ray luminosity than other classical novae detected in \gamma -rays to date , indicating a range of at least a factor of 10 in the \gamma -ray luminosities for these explosions .