Astronomers Are On A Celestial Treasure Hunt. The Prize? Planet Nine : NPR
http://www.npr.org/...3/489815076/astronomers-are-on-a-celestial-treasure-hunt-the-prize-planet-nine
Nobody's actually seen the new planet. The reason astronomers think it's out there is the strange behavior of some
smallish objects in the Kuiper Belt, a collection of celestial objects orbiting in the outer reaches of the solar system.
"The seven most distant of these objects, when they go really far away, they all go in the same direction," says Mike Brown,
professor of planetary astronomy at the California Institute of Technology (Caltech).
That's one hint there's a planet tugging on them, but there are others. "They're all also tilted, compared to the planets in
the solar system," says Brown. "They're tilted about 20 degrees, and they're all tilted in nearly exactly the same direction."
There's a third oddity about these objects: They never come closer to the sun than Neptune, "as if they'd been pulled away from
the sun by something," he says.
