mean planet
noun Astronomy.
a hypothetical planet that coincides with a real planet when the real planet is at perihelion and that moves in an orbit at a constant velocity equal to the mean velocity of the real planet.
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A massive new planet in our solar system named Tyche? Maybe. But what does “Tyche” mean?There may be a new planet joining the solar system. A provocative hypothesis posed by a duo of planetary astronomers from the University of Louisiana-Lafayette includes the existence of the planet Tyche: a ninth planet estimated to be four times the size of Jupiter located somewhere at the outermost reaches of the solar system. It’s hard to know what is more enjoyable: stories about planets …
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Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019