How do astronomers measure the distance to other stars? How accurate are their measurements?
Let G denote the star.. Determine the chord distance between the two positions
The star's distance is approximated by
Observer's distance from the Sun is nearly 1 AU = 149597870 km.
For N days O turns around S through
= N X (360/365.256363) deg
The star's distance
If the precision for angular measurement is 1/1000 deg. N = 30 days will be sufficient for distances of single-digit light years. For larger distances, N has to be increased.
For Alpha Centauri A, at 4.2 ly = 4.2 X 62900 AU from us and with N = 30 days,
For N = 30,