Scientist who killed Pluto now concludes there is a ninth major planet
Enlarge (credit: Caltech/R. Hurt (IPAC))
The demotion of Pluto to dwarf planet didn't come about because of any discovery about Pluto itself. Rather, it was triggered by the discovery that Pluto was one of what's likely to be a large number of bodies that orbit well beyond Neptune. These Kuiper Belt objects (KBOs), some of which are larger than Pluto, tend to have unusual orbits, passing outside of the plane of the Solar System, with their ellipses stretched out on one side, while passing closer to the Sun on the other.
But in recent years, scientists have been noting some odd patterns in the orbits of KBOs. For many of them, their closest approach to the Sun comes as they cross the orbital plane of the inner planets. Now, the researcher who helped identify some of the first KBOs has published a paper in which he identifies a possible cause of these patterns: a distant, Neptune-sized body that would restore our Solar System's planetary total to nine.
Undiscovered planets have a long history, dating back to the prediction of Neptune's existence based on oddities in Uranus' orbit. That success, however, led to a couple of fruitless searches, one for an inner planet that could get Mercury's orbit to behave, and a second for something beyond Neptune. While the latter search turned up Pluto, it was too small to influence Neptune's orbit, which further observations indicated was just fine without any additional fixes.
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