With the VLBA , we have observed water masers associated with the OH/IR star , W43A , which trace a birth and growth of a molecular jet .
The water masers exhibit the collimated distribution ( 1700 AU : 20 AU ) and fast motions ( \pm 150 km s ^ { -1 } ) .
The maser distribution was well fit by a precessing jet model .
The jet length has extended by 800 AU within 8 years , indicating that the extension rate is roughly equivalent to the jet speed ( 150 km s ^ { -1 } ) .
Very likely the jet was born around the year 1960 .
An elongated planetary nebula will be formed by such a jet during an extremely short period ( < < 1000 yrs ) of the transition to form a ptoto-planetary nebula .
Then fading of the water maser jet will be observed during our own life .