A Milliarcsecond-accurate Position for Sagittarius A*

The absolute position of Sgr A*, the compact radio source at center Milky Way, had been uncertain by several tens milliarcseconds. Here we report improved astrometric measurements and proper motion A*. Three epochs phase-referencing observations were conducted with Very Long Baseline Array for A* 22 43 GHz in 2019 2020. Using extragalactic sources submilliarcsecond-accurate positions as reference, determined a reference epoch 2020.0 to be $\alpha$(J2000) = $17^{\rm h} 45^{\rm m}40.^{\rm s}032863~\pm~0.^{\rm s}000016$ $\delta$(J2000) $-29^{\circ} 00^{\prime} 28.^{''}24260~\pm~0.^{''}00047$, an updated $-3.152~\pm~0.011$ $-5.586~\pm~0.006$ mas yr$^{-1}$ easterly northerly directions, respectively.