Astronomers are still searching for a hypothetical Planet Nine in the distant reaches of the Solar System, but an 11-Jupiter-mass planet called HD 106906b is looking more and more like the Planet Nine of its planetary system. HD 106906b occupies an unlikely orbit around a double star 336 light-years away and it may be offering clues to something that might be much closer to home: a hypothesized distant member of our Solar System dubbed Planet Nine....