# How do astronomers measure the distance to other stars? How accurate are their measurements?

##### 1 Answer

Parallax

#### Explanation:

Let G denote the star.. Determine the chord distance between the two positions

Use the

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,