Published online by Cambridge University Press: 30 August 2012
We report trigonometric parallx measurements for H2O masers around the protoplanetary nebula OH 231.8+4.2 carried out with the Very Long Baseline Array. Based on astrometric monitoring for 1 year, we measured a trigonometric parallax of 0.89 ± 0.04 mas, corresponding to a distance of 1.12+0.05−0.05 kpc. This is the most accurate distance to OH 231.8+4.2, and the first one based on an annual parallax measurement. The distribution and internal motions of the H2O masers are consistent with the bipolar outflow suggested in literatures.