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Could 'Planet X' Still be Lurking Out There?

The hunt for the hypothetical Planet X has been fruitless so far, but that doesn't mean astronomers are calling it off.

March 28, 2014
11:30 AM EDT
Orbit diagram for the outer solar system. The sun and terrestrial planets are at the center. The orbits of the four giant planet Jupiter, Saturn, Uranus and Neptune are shown by purple solid circles. The Kuiper Belt (including Pluto) is shown by the dotted light blue region just beyond the giant planets. Sedna's orbit is shown in orange while 2012 VP113's orbit is shown in red. Both objects are currently near their closest approach to the sun. They would be too faint to detect when in the outer parts of their orbits. | Scott S. Sheppard: Carnegie Institution for Science