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Using the Very Long Baseline Array, we have measured a trigonometric parallaxfor the micro quasar GRS 1915+105, which contains a black hole and a K-giantcompanion. This yields a direct distance estimate of 8.6 (+2.0,-1.6) kpc and arevised estimate for the mass of the black hole of 12.4 (+2.0,-1.8) Msun. GRS1915+105 is at about the same distance as some HII regions and water masersassociated with high-mass star formation in the Sagittarius spiral arm of theGalaxy. The absolute proper motion of GRS 1915+105 is -3.19 +/- 0.03 mas/y and-6.24 +/- 0.05 mas/y toward the east and north, respectively, which correspondsto a modest peculiar speed of 22 +/-24 km/s at the parallax distance,suggesting that the binary did not receive a large velocity kick when the blackhole formed. On one observational epoch, GRS 1915+105 displayed superluminalmotion along the direction of its approaching jet. Considering previousobservations of jet motions, the jet in GRS 1915+105 can be modeled with a jetinclination to the line of sight of 60 +/- 5 deg and a variable flow speedbetween 0.65c and 0.81c, which possibly indicates deceleration of the jet atdistances from the black hole >2000 AU. Finally, using our measurements ofdistance and estimates of black hole mass and inclination, we provisionallyconfirm our earlier result that the black hole is spinning very rapidly.

A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass