We have used the Japanese VLBI array VERA to perform high-precision astrometry of an H _ { 2 } O maser source in the Galactic star-forming region NGC 281 West , which has been considered to be part of a 300-pc superbubble .
We successfully detected a trigonometric parallax of 0.355 \pm 0.030 mas , corresponding to a source distance of 2.82 \pm 0.24 kpc .
Our direct distance determination of NGC 281 has resolved the large distance discrepancy between previous photometric and kinematic studies ; likely NGC 281 is in the far side of the Perseus spiral arm .
The source distance as well as the absolute proper motions were used to demonstrate the 3D structure and expansion of the NGC 281 superbubble , \sim 650 pc in size parallel to the Galactic disk and with a shape slightly elongated along the disk or spherical , but not vertically elongated , indicating the superbubble expansion may be confined to the disk .
We estimate the expansion velocity of the superbubble as \sim 20 km s ^ { -1 } both perpendicular to and parallel to the Galactic disk with a consistent timescale of \sim 20 Myr .