Question

Describe the parallax method to measure the distance of a distant star

Answer 1

Parallax is the best way to get distance in astronomy because it does not involve physics; rather, it relies solely on geometry. The method is based on measuring two angles and the included side of a triangle formed by the star, Earth on one side of its orbit and Earth six months later on the other side of its orbit.

Astronomers can measure a star's position once, and then again 6 months later and calculate the apparent change in position. The star's apparent motion is called stellar parallax. The distance d is measured in parsecs and the parallax angle p is measured in arcseconds.