How does the parallax angle relate to distance?

1 Answer
Nov 18, 2015

Parallax is a reliable method for measuring the distance to stars relatively close to the earth.


In the picture below, you can see how parallax is used to determine the distance to a star. First the apparent position of the star in June and in December is noted. A line is then drawn between the earth's position in this months and the center of the sun. this straight line will become the base of a triangle. Next a diagonal line is drawn from each end of the base line to the apparent position of the star in June and in December.These three lines form a triangle. The tip of the triangle is the true position of the star to the base of the triangle. The line labeled D, is the actual distance to the star. *Since astronomers can determine the angles within the parallax triangle, they can calculate the line D. In this way, they can accurately measure the true distance from the earth to the star.