  We study the effects of exceptionally light QCD axions on the stellar
configuration of white dwarfs. At finite baryon density, the non-derivative
coupling of the axion to nucleons displaces the axion from its in-vacuum
minimum which implies a reduction of the nucleon mass. This dramatically alters
the composition of stellar remnants. In particular, the modifications of the
mass-radius relationship of white dwarfs allow us to probe large regions of
unexplored parameter space without requiring that axions are dark matter.
