Two astronomers argue that the farthest objects in the Kuiper Belt are being pushed and pulled by the gravity of Planet Nine, a giant planet orbiting over 10 times farther from the Sun than Neptune. If they find it, it’ll be the first real expansion of the Sun’s planetary album in 170 years. PRODUCTION CREDITS Produced and Directed by: Caitlin Saks and Terri Randall Camera: Dave Arabia Digital Producer: Ana Aceves MEDIA CREDITS Additional Footage: Adler Planetarium, Joe Tucciarone, ESO/A. Santerne, Ed Bell Media, National Astronomical Observatory of Japan, Mike Brown, Konstantin Batygin Music: APM © WGBH Educational Foundation 2019