astronomical parallax

Astronomical parallax is the apparent shift in a nearby star's position against distant background stars as Earth orbits the Sun. Imagine holding out your finger and viewing it with one eye closed, then switching eyes; your finger appears to move relative to distant objects. Similarly, as Earth moves around the Sun over a year, nearby stars seem to change position slightly. By measuring this tiny shift—called the parallax angle astronomers can determine the star's distance, with larger shifts indicating closer stars. This method is fundamental for establishing the scale of our galaxy and understanding stellar locations.