Planet 9

[Jitendra Hydonus]

Evidence he and others have gathered over the past decade suggests something strange is happening in the outer solar system: distant subplanetary objects are being found on orbits that look sculpted, arranged by an unseen gravitational force. According to Brown, that force is coming from a ninth planet—one bigger than Earth but smaller than Neptune.

https://www.scientificamerican.com/article/if-planet-nine-exists-well-find-it-soon/