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A comment on Seven earth-sized planets discovered circling a star 39 light years from Earth. Parent comment

Re:Seven earth-sized planets discovered circling a star 39 l... by gozur88 on Wednesday February 22, 2017 @03:30PM (#13708883)
It's not a given, though. We used to think Mercury is tidal locked, but that turns out not to be the case. These planets, as I understand it, are in similar orbits, so they may not be locked either.
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Re:Seven earth-sized planets discovered circling a star 39 l... by aetherson on Wednesday February 22, 2017 @04:41PM (#13709425)
Well, Mercury is in a tidally locked orbit of sorts. Its rotation is resonant with its orbit -- it experiences two days every three years, and this isn't a coincidence, it's a relatively stable outcome of its tidal forces with the sun.
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