A Stationary Core with a One‐sided Jet in the Center of M81

(accepted for publication in the Astrophysical Journal) The nucleus of the nearby spiral galaxy M81 was observed at 8.3 GHz with a global VLBI array at 20 epochs over four and a half years, with a linear resolution at the source of about 2000 AU or 0.01 pc. Phase-referenced mapping with respect to the geometric center of supernova 1993J in the same galaxy enabled us to find, with a standard error of about 600 AU, a stationary point in the source south-east of the brightness peak. We identify this point as the location of the core and the putative black hole at the gravitational center of the galaxy. The 2σ upper bound on the core’s average velocity on the sky is ≤ 40 µas yr −1 or ≤ 730 km s −1 (relative to the center of SN1993J, in excess of galactic rotation). A short, one-sided jet extends towards the north-east from the core, in projection approximately in line with the rotation axis of the galaxy, and towards the well-known extended emission 1 kpc further out. The orientation of the jet varies smoothly, with timescales of about one year, and an rms of 6 ◦ , around its mean position angle of 50 ◦. Occasionally the jet appears to bend to the east. The