A new study has proposed the existence of Planet Y, an alternative Planet Nine candidate that is smaller and closer to Earth than the hypothetical Planet X, which astronomers have been hunting for almost a decade. However, the evidence for this newly theorized world is "not definitive."
Prof. Sam Lawler, cited in the article as a critic/skeptic, is very active on Mastodon @sundogplanets@mastodon.social and interesting to follow.