![21PLANET-master1050-v2](https://static.wixstatic.com/media/beba04_1c428353d1ae4700bc4040c0f4f4f89b~mv2.jpg/v1/fill/w_147,h_83,al_c,q_80,usm_0.66_1.00_0.01,blur_2,enc_auto/beba04_1c428353d1ae4700bc4040c0f4f4f89b~mv2.jpg)
An artist’s impression of a possible ninth planet. It would be quite large — at least as big as Earth — with a thick atmosphere around a rocky core. CreditCalifornia Institute of Techonology
Caltech scientists Konstantin Batygin and Mike Brown make the case for Planet Nine, a giant planet tracing a bizarre, highly elongated orbit in the outer solar system.