  We present proper motions of water masers toward the Onsala 1 star forming
region, observed with the Japanese VLBI network at three epochs spanning 290
days. We found that there are two water maser clusters (WMC1 and WMC2)
separated from each other by 1".6 (2900 AU at a distance of 1.8 kpc). The
proper motion measurement reveals that WMC1 is associated with a bipolar
outflow elongated in the east-west direction with an expansion velocity of
69+-11 km/s. WMC1 and WMC2 are associated with two 345 GHz continuum dust
emission sources, and located 2" (3600 AU) east from the core of an
ultracompact HII region traced by 8.4 GHz radio continuum emission. This
indicates that star formation activity of Onsala 1 could move from the west
side of ultracompact HII region to the east side of two young stellar objects
associated with the water masers. We also find that WMC1 and UC HII region
could be gravitationally bound. Their relative velocity along the line of sight
is 3 km/s, and total mass is 37 Mo. Onsala 1 seems to harbor a binary star at
different evolutionary stage.
