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How flat can a planet be? (Synopsis)

14 Feb 2017, 20:11 UTC
How flat can a planet be? (Synopsis) NASA
(200 words excerpt, click title or image to see full post)

“‘I’ll follow him to the ends of the earth,’ she sobbed. Yes, darling. But the earth doesn’t have any ends.” -Tom Robbins
We have some pretty good definitions of what it takes to be a planet, and one part of that definition is that a world needs to be massive enough to pull itself into hydrostatic equilibrium. In the absence of external forces and rotation, that means it will be a perfect sphere.
The line for a planet vs. a non-planet is mass-dependent, and making a thin, rigid body fails on that account. You can have a flat “thing” in space, but it wouldn’t be a planet if you did. Image credit: Margot (2015), via http://arxiv.org/abs/1507.06300.
But what about if you allow the other forces to come into play? In addition to the many interesting features you’ll get, one of them is a flattening of your world. So that brings up the question of how flat a planet could possibly be? This isn’t just theory; our own Solar System has a great example that you’ll want to see for yourself!
A model of Haumea rotating, based on the most accurate data available. Image credit: Wikimedia Commons user Stephanie Hoover.
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