Return to Astronomy Index PageParallax
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Parallax is the geometric process by which astronomers used to figure distances to stars. Astronomers photograph a star at point A and the photographic a star six months later at point A'. Then they measure the change in the parsecs between the two photographs of the same star. Using the formula d = 1/P distance can be found to the star.
Sample Problem:
If a stars measures 2 parsecs what is its distance from Earth?
One parsec equals 206,265 AU or 3.26 ly
d = 1/P d is unknown distance, P is 2
d = 1/2
d =.5 pc
Then multiply .5 pc by 3.26 ly = 1.63 ly from Earth (Answer)