The Evidence for Planet Nine’s Existence
Why do some astronomers think there’s a massive planet on the edge of our solar system?
By Ana Aceves and Caitlin Saks
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.