The isolated neutron star RX J185635-3754 is the closest known neutron star to the Sun .
Based on HST WFPC2 obervations over a 3 year baseline , I report its proper motion ( 332 \pm 1 mas yr ^ { -1 } at a position angle of 100.3 ^ { \circ } \pm 0.1 ^ { \circ } ) and parallax ( 16.5 \pm 2.3 mas ; 61 pc ) .
This proper motion brings the neutron star from the general vicinity of the Sco-Cen OB association .
For an assumed neutron star radial velocity between - 55 and - 60 km s ^ { -1 } , the runaway O star \zeta Oph , the Upper Sco OB association , and the neutron star come into spatial coincidence between 0.9 and 1.0 million years ago .
RX J185635-3754 may be the remnant of the original primary of the \zeta Oph system .
If so , the space velocity suggests that the neutron star received a kick of about 200 km s ^ { -1 } at birth .