  We report on the detection in the combined $Gaia$-DR1/RAVE data of a lack of
disk stars in the solar neighbourhood with velocities close to zero angular
momentum. We propose that this may be caused by the scattering of stars with
very low angular momentum onto chaotic, halo-type orbits when they pass through
the Galactic nucleus. We model the effect in a Milky-Way like potential and fit
the resulting model directly to the data, finding a likelihood
($\sim2.7\sigma$) of a dip in the distribution. Using this effect, we can make
a dynamical measurement of the Solar rotation velocity around the Galactic
center: $v_{\odot}=239\pm9$ km s$^{-1}$. Combined with the measured proper
motion of Sgr A$^*$, this measurement gives a measurement of the distance to
the Galactic centre: $R_0=7.9\pm0.3$ kpc.
