Radio imaging of the microquasar GRS 1915+105 with the Very Long Baseline Array ( VLBA ) over a range of wavelengths ( 13 , 3.6 , 2.0 and 0.7 cm ) , in different states of the black hole binary , always resolves the nucleus as a compact jet of length \sim 10 \lambda _ { cm } AU .
The nucleus is best imaged at the shorter wavelengths , on scales of 2.5 - 7 AU ( 0.2 - 0.6 mas resolution ) .
The brightness temperature of the core is T _ { B } \geq 10 ^ { 9 } K , and its properties are better fit by a conically expanding synchrotron jet model , rather than a thermal jet .
The nuclear jet varies in \sim 30 min during minor X-ray/radio outbursts , and re-establishes within \sim 18 hours of a major outburst , indicating the robustness of the X-ray/radio ( or disk/jet ) system to disruption .

At lower resolution ( 80-240 AU ) , more extended ejecta are imaged at \sim 500 AU separation from the stationary core .
Time-lapse images clearly detect the superluminal motion of the ejecta in a few hours .
The measured velocity is 1.5 \pm 0.1 c ( D/12 kpc ) for the approaching component , and is consistent with ballistic motion of the ejecta from 500 AU outwards , perhaps even since birth .
The axis of the ejecta differs by \leq 12 ^ { \circ } clockwise from the axis of the AU-scale jet , measured in the same observation .
Both axes are stable in time ( \pm 5 ^ { \circ } ) , the AU scale for two years , and the large scale for over four years .
Astrometry over two years relative to an extragalactic reference locates the black hole to \pm 1.5 mas , and its secular parallax due to Galactic rotation is 5.8 \pm 1.5 mas yr ^ { -1 } , consistent with a distance of 12 kpc .
Finally , a limit of \leq 100 km s ^ { -1 } is placed on its proper-motion with respect to its neighbourhood .

Some accreting black holes of stellar mass ( e.g .
Cyg X-1 , 1E 1740-2942 , GRS 1758-258 , GX 339-4 ) and supermassive black holes at the centre of galaxies ( e.g .
Sgr A ^ { * } ) lack evidence of large flares and discrete transient ejecta , but have compact radio cores with steady , flat-spectrum ‘ plateau ’ states , like GRS 1915+105 .
Until now GRS 1915+105 is the only system where both AU-scale steady jets and large-scale superluminal ejections have been unambiguously observed .
Our observations suggest that the unresolved flat-spectrum radio cores of accreting black holes are compact quasi-continuous synchrotron jets .