Astronomers notice that a known planet, or a bunch of comets, begin moving in ways Newton's laws of motion can't explain.
They propose that it's caused by the gravity of something massive and still undiscovered lurking out in the Solar System, and they head to their telescopes to search for it.
Most often it's all a big mistake; the unexplained motion turns out to be just an incorrect measurement. (The great exception concerned Neptune, spotted in 1846 after observers noticed Uranus wandering from its predicted path).
So when a pair of University of Louisiana astronomers, writing in the journal Icarus, advanced their recent theory about a new mystery planet in our solar system -- and a very, very big one -- their colleagues mostly just listened politely, then went back to work. More>>
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