In DepthAstronomy

New haul of distant worlds casts doubt on Planet Nine

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Science  23 Jun 2017:
Vol. 356, Issue 6344, pp. 1221
DOI: 10.1126/science.356.6344.1221

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In early 2016, astronomers made a bold claim: an unseen giant the size of Neptune lurked in the farthest reaches of the solar system. They couldn't see it directly, but inferred its existence by the way that its gravity had shaped and clustered the orbits of a half-dozen distant icy worlds. Since then, the case for Planet Nine has been bolstered by other evidence, such as a peculiar tilt to the sun's spin axis, along with a few more of these strange objects, which have elongated orbits of more than 4000 years and never come closer to the sun than Neptune. Now, a survey has found four more of these extreme bodies, but they don't display the tell-tale clustering. It's not a crippling blow to the Planet Nine hypothesis, but it raises doubts.