Planet Nine’s existence is not the first time astronomers have predicted a planet they couldn’t see. Clyde Tombaugh was looking for Planet X when he accidentally found Pluto. After Voyager 2 flew by Neptune in 1989, new calculations determined there was no Planet X. But three years ago, a disturbance was detected at the far reaches of the Solar System.

PRODUCTION CREDITS

Produced and Directed by Caitlin Saks and Terri Randall

Camera Dave Arabia

Digital Producer Ana Aceves

MEDIA CREDITS

Additional Footage: Adler Planetarium, IAU, Joe Tucciarone, Ed Bell Media, Alden Tombaugh, NASA/Public Domain, Konstantin Batygin

Music: APM

© WGBH Educational Foundation 2019