What's VERA ?
VERA's Target Accuracy
The diameter of the Galaxy's disk is estimated to be about 100,000 light years. Thus, the annual parallax of stars in the Galaxy is very small, and it is not easy to detect. VERA will measure positions of stars with 10-micro-arcsec level accuracy (1/360,000,000 degree), and will allow us to measure the parallax in the whole Galaxy's disk.
10-micro-arcsec corresponds to a apparent size of 1-JPYen coin (2cm in diameter) on the moon, viewed from the Earth !
with 10 micro-arcsec accuracy, VERA can determine distances within the entire Galaxy's disk. The outer circle corresponds to the area with distance determination error less than 20 %, which covers the whole Galaxy's disk.