Here's how it works:

* Imagine holding your finger out in front of your face and closing one eye, then the other. Notice how your finger appears to shift position relative to the background.

* Stars are so far away that we don't see this shift with our naked eye. However, astronomers use telescopes and measure the tiny shift in a star's position as Earth orbits the Sun. This shift is called parallax.

* The larger the parallax angle, the closer the star is to us. The smaller the parallax angle, the farther away the star.

Parallax is a fundamental tool in astronomy for measuring the distances to nearby stars.