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Even if there are multiple undiscovered planets, there would be at most one planet nine, plus maybe a planet ten, eleven, etc.
by tobr 8y ago
Even if there are multiple undiscovered planets, there would be at most one planet nine, plus maybe a planet ten, eleven, etc.
- dotancohen 8y agoWhat would happen if we discover an object that deserves the term "planet" at 180 AU, and then five years later discover another at 120 AU? Which one is "nine"?
- ahje 8y agoBoth. The one at 180 AU would be considered the 9th known planet from the Sun, until the one at 120 AU was discovered.