The eccentric WR+O binary system WR 140 produces dust for a few months at intervals of 7.94 yrs coincident with periastron passage .
We present the first resolved images of this dust shell , at binary phases \phi \sim 0.039 and \sim 0.055 , using aperture masking techniques on the Keck-I telescope to achieve diffraction-limited resolution .
Proper motions of approximately 1.1 milliarcsecond per day were detected , implying a distance \stackrel { < } { { } _ { \sim } } 1.5 kpc from the known wind speed .
The dust plume observed is not as simple as the “ pinwheel ” nebulae seen around other WR colliding wind binaries , indicating the orbital plane is highly inclined to our line-of-sight and/or the dust formation is very clumpy .
Follow-up imaging in the mid-infrared and with adaptive optics is urgently required to track the dust motion further , necessary for unambiguously determining the orbital geometry which we only partially constrain here .
With full knowledge of the orbital elements , these infrared images can be used to reconstruct the dust distribution along the colliding wind interface , providing a unique tool for probing the post-shock physical conditions of violent astrophysical flows .