What once looked like evidence for a giant planet hiding at the solar system's edge may be an illusion, a study suggests. "We can't rule it out," says Kevin Napier, a physicist at the University of Michigan in Ann Arbor. "But there's not necessarily a reason to rule it in." Previous work has suggested that a number of far-out objects in the solar system cluster in the sky as if they are being shepherded by an unseen giant planet, roughly 10 times as massive as Earth. Astronomers dubbed the invisible world Planet Nine or Planet X. A new analysis of 14 of those bodies shows no evidence for such clustering, Napier and colleagues report online February 10 at arXiv.org in a paper to appear in the Planetary Science Journal.
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