Parallax and proper motion

Simulated motion of a star in the sky caused by the combination of parallax, an apparent shift caused by Earth’s yearly motion around the Sun, and proper motion, which results from the star’s true motion through the Galaxy. Parallax and proper motion have been exaggerated by 10 000 times to make it visible in this animation, which shows the star’s position in the sky for about three and a half years.

Astronomers need accurate measurements over more than one year to separate the parallax from the stars’ true movements.

ESA’s Gaia satellite has observed more than one billion stars, measuring their positions, parallaxes and motions across the sky to unprecedented accuracy.