How do you measure the distance between two stars?

If the pair of stars are only a few light years away from us, the distance between them is measured by the so-called trigonometric parallax. The principle is simple: place your thumb close to your nose and alternately wink your eyes. You will notice that the thumb moves from left to right relative to the background. If you repeat the operation with the arm extended, you will see that the thumb displacement or parallax is less. This works the same way for stars, but instead of the eyes, two satellites are used. Knowing the distance between these and the parallax of each star, the astronomer calculates the distance at which the two stars are from us. These measurements can also be obtained by spectrometry. With these data, the distance between the pair of stars is found by means of a simple triangular mathematical formula r.