Parallax

Simulated motion of a star in the sky due to parallax, an apparent shift caused by Earth’s yearly motion around the Sun. The parallax has 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.

Measuring parallaxes is very complex because we observe this apparent motion combined with the true motion of stars through the Galaxy. 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.