Definition of A Double Planet
There has been some debate in the past on precisely where to draw the line between a double-planet and a planet–moon system. In most cases, this is not an issue because the satellite has a small mass relative to its host planet. In particular, with the exception of the Earth–Moon and Pluto–Charon systems, all satellites in the Solar System have masses less than 0.00025 (1⁄4000) the mass of the host planet or dwarf planet. On the other hand, the Moon to Earth mass ratio is 0.01230 (≈ 1⁄81), while the Charon to Pluto mass ratio is 0.117 (≈ 1⁄9).
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“I’m beginning to think that the proper definition of “Man” is “an animal that writes letters.””
—Lewis Carroll [Charles Lutwidge Dodgson] (1832–1898)
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—Ana Castillo (b. 1953)
“The obsession with suicide is characteristic of the man who can neither live nor die, and whose attention never swerves from this double impossibility.”
—E.M. Cioran (b. 1911)
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