Signs point to Planet 9

We may have found the first direct evidence of a ninth major planet in the Solar System

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Suggestions of a ninth planet in our Solar System have been rumbling on for years now. Some astronomers argue that the clustering and orbital tilt of a group of trans-Neptunian objects indicate gravitational shepherding by an unknown planet. This hypothetical Planet 9, probably similar to Neptune, has been calculated to be on an elliptical orbit coming to around 300 AU (1 AU is the Earth-Sun distance). However, despite several surveys, no such remote new planet has been spotted, and the claim remains controversial.

This lack of observational evidence isn't itself a damning outcome. The predicted orbit for Planet 9 is at least 10 times further from the Sun than Neptune, so the planet would reflect precious little light back to Earth. There's also a large degree of uncertainty around the proposed planet's orbital parameters and therefore exactly where in the sky searches should be targeted. Even if it is out there, Planet 9 would be easy to miss.